I've had my 8310 for a while now but just started playing around with the video player. I've downloaded some avi files and some mp4 files and they all play just fine. I use Format Factory 2.00 to convert my files and it's a great (free) program.
I just want to get some opinions on which format plays back the best. It seems to me that the mp4 format works better than avi because I can get it to go full screen but the quality seems similar. I haven't ever tried to convert to 3gp or to any other formats.
Go to vuclip.com via mobile browser and you can download videos on .3gp format. Make sure your emulation mode is set to blackberry. When you click view hi-res or view lo you can download the video straight to your phone.
Posted from my CrackBerry at wapforums.crackberry.com