I am wondering how many of you register expired domain names to help your sites rank? You can find many at FreshDrop.net - The Domain Searching Platform
Look for the ones with .gov and .edu links
Permanent redirect them to one of your sites when you catch them and voila!

I have seen some good results from that.
You can also run a Welcome to The 404 Checker to find sites listed in high profile directories and see which ones have already been expired.

Have you had any success with this yet?