What Webapp Combinations Work Best Together?

The ReadWriteWeb site lists a few webapp combinations that add up to more than the sums of their parts. In the list: Jott & Evernote (as guest Brad Isaac detailed for us), AideRSS with the ticker-display Snackr, Facebook filtered through Dapper, and other clever ideas. But you’re the folks who actually read about and use the services we write about—so let’s hear some of your own killer combinations. What webapps filter/feed/pipe each other best? Post your link-ups in the comments.