Originally Posted by diwrom
Appbrain will store all of your apps online. This way when you reset or get a new phone you can get them quickly. Usually the Market will only show you the ones you have paid for after a reset. When you download appbrain, you have the option of downloading all of your previous apps..and all at once. You have to be sure to back up appbrain after installing new apps. I do not use it's market, just the feature to save my apps.
Just a note, it's been my experience that if you go into the market right after you do a reset all of your apps are still listed for a short time. I always just fire up the wifi and hit the market right away and get it all back.