I keep a daily log of what I work on, i also drop other info links and notes.

This is mostly to facilitate daily updates in lieu of stand ups.

Another thing I do along side my todo.txt is log important team changes, team switches, people encounters, side projects and any major project milestones that might be useful to point out in my 6 month reviews.

It's really amazing to search back and find links to things you did months ago when search won't pick it up.