A friend of mine from grad school recently suggested a really good idea for a webtool on his blog (it’s a personal blog, so I won’t link there, but he can identify himself in comments if the urge strikes): one should be able to search for theorems based on hypotheses and/or conclusions. So that if you wanted to prove a representation was indecomposible, you could search for theorems where that was the conclusion.
Of course, such a thing would only be functional if it could produce this automatically, which would be a tricky business. On the other hand, computers aren’t as stupid as they sometimes seem. If they can do machine translation, they should be able to do this (eventually). Any Googlers out there looking for something to do in their 20% time?