Don't worry, good solutions are coming!
Couchdb and Hypertable are open source and still in alpha, but they are clearly designed to make scaling on commodity software simple. They work pretty well, and may change how you think about databases.
Also, if it's okay to let someone else do the distributing for you, Google AppEngine and Amazon SimpleDB are extremely cheap distributed database services, though they're both in beta right now so strict limitations are imposed.
