Josiah Bartlett. Signer
of Declaration of Independence, delegate from New Hampshire (Continental
Congresses of 1775-78), free frank "Free J. Bartlett" and address in
his hand on folded cover to William Whipple (Signer and delegate
from N.H.) in Portsmouth N.H., red ms. "Free", "Phila. Sep. 3" straightline
on back, some slight splitting along folds, fresh and Very Fine, Bartlett
was the first person to vote for the Declaration of Independence and the
second to sign it (Image) 
Charles Carroll. Signer
of Declaration of Independence, delegate from Maryland (Continental
Congresses of 1777-77), free frank "Ch Carroll of C free" (Charles
Carroll of Carrollton) on folded cover addressed in his infirm hand to
Louis M. Lane in Wilmington Del., ms. "Browns Tavern June 19" postmark,
minor wrinkles and tiny edge tears, still Very Fine, undated but probably
late (1828-32) -- as the last living Signer, the distinguished Senator
Carroll was the beneficiary of an Act of Congress in 1828 giving him
free-franking privileges for life (which last until 1832) (Image) 
William Floyd. Signer of
Declaration of Independence, delegate from New York (Continental Congresses
of 1774-77 and 1778-83), autograph free frank "Wm. Floyd Free" and
address on large part of folded cover to Samuel Hazard at Newtown Conn.,
the cover has been cleaned, silked and refolded, pencil note indicates that
the letter (no longer present) was dated at Philadelphia on Feb. 14, 1780,
a Fine and attractive example of this scarce Signer's signature, very rare
as a free frank, ex Grunin (Image) 
Elbridge Gerry. Signer of
Declaration of Independence, delegate from Massachusetts (Continental
Congresses of 1776-81 and 1782-85), framer of the Constitution, member of
Congress, Governor of Massachusetts, and Vice President under James
Madison, autograph free frank "free E. Gerry" on small folded over
to Northampton Mass., brownish-black "31/IA" Franklin mark and matching
"Free" handstamp, both of Philadelphia, Very Fine and scarce Signer's free
frank, Gerry's political maneuvering inspired the term "gerrymandering", he
refused to sign the Constitution as he thought it gave the President too
much power (Image) 
Benjamin Franklin. Free
frank as Deputy Postmaster General "Free B. Franklin" on Nov. 25,
1762 folded cover to Mrs. Katherine Green in Rhode Island, some expert
restorationVERY FINE APPEARANCE. A RARE BENJAMIN FRANKLIN FREE FRANK FROM HIS TERM AS DEPUTY POSTMASTER GENERAL FOR THE COLONIES IN AMERICA.
In 1753, Franklin was appointed Deputy Postmaster General for the Colonies in America. He had met the recipient of this letter in 1754 while visiting his family in Boston and had kept up a correspondence with her. In the spring of 1763, some months after sending this letter, Franklin embarked on a six-month tour to inspect his postal domain. While traveling through Rhode Island, he fell and injured his shoulder. Fortunately, Katherine Green and her husband, William, lived close by, and Franklin was able to recover there. Later, when fighting broke out in Boston, Franklin's sister, Jane Mecom, took refuge with Mrs. Green.
Accompanied by a transcript of the letter that originally accompanied this cover (now in the possession of the American Philosophical Society). (Image)
Benjamin Franklin. Free
frank "B. Free Franklin" as Deputy Postmaster for the Colonies on
cover front (restored with flaps) from London and addressed in his hand to
Mrs. Franklin in Philadelphia, also endorsed in his hand "via N York pr.
Packet", red London "Free" in circle handstamp, expert restoration not
affecting writingVERY FINE APPEARANCE. A HIGHLY DESIRABLE FORM OF BENJAMIN FRANKLIN'S FREE FRANK WITH THE "B. FREE FRANKLIN" SYNTAX. THIS MAIL WAS SENT TO HIS WIFE FROM ENGLAND AND CARRIED FREE OF PACKET CHARGES AND INTERNAL POSTAGE.
This was most likely mailed in 1772, during Franklin's residence in London. With 1983 Charles Hamilton certificate. (Image)
Benjamin Franklin. Free
frank "B Free Franklin" as Continental Postmaster General on
folded cover addressed to Col. Bull of the Pennsylvania Forces at Perth
Amboy N.J., neat "Phila Aug. 27" (1776) straightline datestamp, skillfully
restoredFINE APPEARANCE. AN EXTREMELY RARE BENJAMIN FRANKLIN FREE FRANK AS POSTMASTER GENERAL OF THE CONTINENTAL POST WITH THE "B. FREE FRANKLIN" SYNTAX USED LESS THAN ONE MONTH AFTER THE SIGNING OF THE DECLARATION OF INDEPENDENCE.
On July 26, 1775, the Continental Congress established the position of Postmaster General of the United Colonies and appointed Benjamin Franklin to the post. Slightly less than a year later, the Declaration of Independence was signed. He left for his historic trip to France shortly after this letter was mailed. Examples of Franklin's signature as Continental Postmaster General are extremely rare in any form, and this could be the only free frank in private hands.
Ex E. N. Sampson. (Image)
Benjamin Franklin.
Incoming letter addressed to "Dr. Franklin, Craven Street in the Strand,
London", originally rated "6" pence due but crossed out and sent free
of charge, red London "Free" in circle handstamp, red "JA/30" and "3/FE"
Bishop's marks, ms. receipt docketing "Dr. Robertson 1770" on flap
(almost certainly in Franklin's own hand), some wear, opened for display of
all markings and docketing, Very Fine, sent from the president of Edinburgh
College to Franklin during his term as Deputy Postmaster General, which
allowed him to send and receive mail free of charge
(Image) 
Lyman Hall. Signer of the
Declaration of Independence, delegate from Georgia (Continental Congresses
of 1775-78, 1780), Governor of Georgia, free frank "Free Lyman Hall"
and address on folded cover to Elnathan Street Jr. at Wallingford Conn.,
ms. "Free" in another hand, with straightline "Phila Sep. 28" (ca. 1776) on
back, skillfully cleaned to lighten foxing, manuscript strengthened in
placesA VERY RARE EXAMPLE OF THIS SIGNER'S SIGNATURE AND POSSIBLY THE ONLY FREE FRANK IN PRIVATE HANDS.
This style of Philadelphia straightline is recorded from June 26, 1776, to August 12, 1777. The British occupied Philadelphia from September 26, 1777, until June 18, 1778, during which time the Congress met at Lancaster (one day only) and York (Town), Pennsylvania. Use of this postal marking in September points to a 1776 year date.
Ex Stevens (Siegel Sale 556, realized $5,250) and illustrated in his article on free franks of the Continental Congress, ex Grunin (Siegel Sale 750, realized $6,250) (Image)
John Hancock. Signer of
Declaration of Independence, delegate from Massachusetts, bold free frank
"John Hancock" on folded letter "To His Excellency Commodore
Destouche, Commanding the Fleet &c &c, Newport", also endorsed
"Public Service", faint vertical file fold does not affect
frankingVERY FINE. A SCARCE AND DESIRABLE FREE FRANK FROM JOHN HANCOCK DURING THE REVOLUTIONARY WAR.
This cover to the Commander of the French fleet at Newport would have been sent during the second half of 1780 or in early 1781.
Ex Stevens (Image)
John Hancock. Signer of
Declaration of Independence, delegate from Massachusetts, free frank
"Congress Baltimore John Hancock" as President of Third
Continental Congress (Dec. 20, 1776 to Mar. 4, 1777) on folded cover
addressed in his hand to "The Hon. The Council of Safety of the State of
Pennsylvania", receipt docketing on flap indicates Jan. 9, 1777 origin
date and enclosure of a Resolve of Congress, lightly toned file folds,
expertly silked and restoredVERY FINE APPEARANCE. A RARE JOHN HANCOCK FREE FRANK AS PRESIDENT OF THE THIRD CONTINENTAL CONGRESS, THE ONLY CONGRESS TO BE CONVENED IN BALTIMORE.
After the retreat of the Continental army through New Jersey, Congress was apprehensive of an attack on Philadelphia and adjourned on December 12 to meet later in Baltimore, from December 20, 1776, to March 4, 1777. This cover was franked and sent during that time period. (Image)