The problem I have with so many tips/tricks/hacks going through my virtual periphery these days is sometimes I will read something, forget it, and then later remember it. Here are a few things I've recently remembered.
Gmail: By adding a +word to your gmail address, you can keep track of where people are getting your email address from. So if my email is taylor@gmail.com you can make it taylor+citibank@gmail.com to track if Citibank really isn't selling your email address to others. Worse case they are, you can set a filter to send all those emails to the spam folder.
Photoshop: I have a Digital Rebel XT that embeds lovely EXIF metadata (like ISO, shutter speed, focal length etc etc) automatically into the jpg. The problem is after you adjust it in photoshop and use Save For Web it deletes all that data. Use the normal Save as.. instead!
AIM: Add "SmarterChild" to your buddy list, and you can get definitions quickly. Just IM him "def university for a definition of university.This is great for quick spell checking because if you misspelled it, SmarterChild suggests a few possible spellings for you. Of course you can get the weather, thesaurus, and have a one sided conversation with him too.
What have you un-forgotten?