OK, I have had the following results, when connecting to my phone from the xbox 360 user interface, without too much tinkering. Note that I am using the DROID2
Music: I am able to browse the folder structure, and stream from the phone to the xbox successfully. (I'm a bit shocked this worked)
Pictures: I am able to browse the folder structure, but none of the images would play on my xbox. This is not a format issue, since the photos on my phone are a combination of droid photos and other photos I took from my DSLR. All of these photo can be viewed by my xbox when served from windows media player library using DLNA
Video: The xbox360 can find the droid, and I can view the folders, but no videos are available.
The xbox is hard wired to the same Cisco Wireless router my droid is connected to on wifi.
Again, I haven't tinkered much, but since this is a use case that I will probably never need, I am going to quit trying. I use DLNA fairly extensively in my home, and can't really see a scenario when I will need to serve from my phone. It's a cool concept, but not that useful IMHO.