One of the things I like to do is re-work and improve comments I have left in forums or on other blogs into posts on this blog. I have been using Backtype for a few weeks now and have found it useful for keeping track of other places I have commented. You need to register and claim comments under various aliases that comment systems require you to use (e.g. my skmurphy e-mail, my Gmail account, Hacker News ID, etc..).
For a list of my recovered comments see http://www.backtype.com/skmurphy
Update Sat-Apr-24-2010: Useful while it lasted, it looks like Backtype has changed direction to focus on real time search and is no longer archiving comments older than three months. If you are aware of a tool that offers Backtype’s old comment tracking and archive capability I am happy to pay $10-25/month for this capability, depending upon the functionality set. I offered to pay Backtype $100-$200 a year to preserve this functionality but there are apparently too few folks like myself.