One of the best coin collector's resources on the web is the U.S. Mint site, which shows all available coins you can purchase online or order through a catalog. Some coins have limited mintage and other are only available for limited times.
Collectors who dillydallied this year were denied some of the silver dollars commemorating the 300th anniversary of Ben Franklin's birth. All four available coins sold out quickly, so it's important not to delay in ordering the coin you want.
New coins recently made available are proof sets of the five state quarters that will be released in 2006: Nevada, Colorado, Nebraska, and the Dakotas. The entire set is $15.95 and the silver proof is $23.95
I glad that most coins celebrate their dates retroactively and not at the actual time the event occurred. Things would get pretty awkward if there was a "Celebrating 50 years of Slavery" or "Pullman Strike Righteously Quashed Anniversary Set" coin out there.