If you've waited since 1607 to celebrate your 400th birthday, starting a tiny bit early seems forgivable.
Jamestown, Virginia, is kicking off its birthday festivities this coming May, and will host 18 months of events. Most activities are free and open to the public. The replica ship Godspeed will be cruising the Eastern Seaboard this spring and summer, stopping in Baltimore, Philadelphia, New York, Boston, and Newport to bring a taste of ye olde birthday to the Mid-Atlantic and Northeast.
For more information or a list of events, check the Jamestown 2007 site.