Yeah, you have to have a rooted phone for this to work. It hasn't happened on the droid yet and it's what i'm waiting for and the main reason I rooted. This was possible on my tmobile g1. There were guides on how to do it and a lot of the custom roms would have it built in, especially the roms by Cyanogen. He put out some great roms. Even had his own updater that would alert you when he had an update to the rom. The internal file system of the droid is an ext3 or ext4 file system. I believe thats right. Anyway, the apps wont work on the fat32 file system that the sd cards are formated in. In order to do it on the g1, you would have to reformat your sd card into 2 different partitions. I generally allocated 1g to the ext3 file system and the rest to storage in the fat32 file system. So, on my g1 I had 1g of space to install apps. Now, the problem is, the sd cards that came with the Droids are class 2. For those that don't know, the class is how fast information is able to be read off the card. The guides recommended a class 6 sd card which of course is more expensive. A class 2 could cause glitches and serious lag of running apps. I ran a class 4 with pretty much no problems. The first time I did it there were no roms with it automatically built in so I had to follow a guide with a lot of terminal commands. Basically, you move a few folders from the phone over to the new partition of the sd card and then link them back to the phone so that the apps are installed to the sd card. It was pretty simple if you were comfortable with entering commands but as all mods it could brick your phone. I'm surprised one of the great "mod'ers" hasn't already done this. I'm already almost out of space on my droid and really don't want to delete any of the apps I have installed.