This coming Saturday is the bicentenniel of Lewis and Clark's return to St. Louis after their voyage of discovery that extended white America's knowledge of this continent to the Pacific ocean. With that in mind, I'd certainly recommend Lewis and Clark: What Else Happened.
This blog not only provides daily updates (save for a period of time when New Orleans, the source of the blog, was underwater) from the Journals of Lewis and Clark, but also provides historical tidbits about what else was happening elsewhere in the world while the captains were on their two and a half year adventure.
I've actually made it through most of Lewis and Clark's Journals, so I look forward to exploring this site a bit more thoroughly. The Resources page on the site gives a number of jumping off points to find out more about the expidition.
NP: "New Dawn Fades (Live)" - Joy Division