Two-dollar bills have been issued by the United States in one form or another since 1862 and still exist as Federal Reserve Notes, though they are not commonly circulated. As collectors' items, they have a wide variety of values depending on age, condition, rarity and collector demand.
Before 1928, U.S. currency, including $2 notes, was larger than it is today (7.42 by 3.12 inches). These $2 notes came in a large variety between 1862 and 1928: United States Notes, Silver Certificates, Treasury Notes and one Federal Reserve issue (in 1917).
Large Note Values
Considering the variety, there's no standard pricing for pre-1928 $2 notes. Most circulated examples will be valued less than $100 (probably considerably less), though some uncirculated notes might be worth hundreds and rarities even more.
After 1928, both U.S. Notes (red seal) and Federal Reserve Notes (green seal) were made their current size. Two-dollar bills have been issued since then in relatively small quantities, but few command high prices.
$2 U.S. Notes
U.S. Notes in the $2 denomination in average condition are typically worth from face value to a few times face value, with 1928B being the exception, and the most expensive, up to $85. In uncirculated condition, $2 U.S. Notes are worth a lot more--50 to 100 times face value in some cases and $700 for the 1928B.
$2 Federal Reserve Notes
Series 1976 and 1995, $2 Federal Reserve Notes are worth face value in average condition and perhaps two times face value in uncirculated condition.
Star notes are those with a star (asterisk) after the serial number. A star note replaced the original note, which was defective in some way and thus destroyed, during the manufacturing process. Being a star note usually adds value to a $2 bill, but especially to already rare notes in uncirculated condition. Pristine 1928B star notes, for instance, have sold for more than $13,000.