To save myself some time as well as an extremely long forum post, please just click the following link and it should answer your questions about submission rules as well as how you can submit a movie. http://movies.nfsunlimited.net/submitmovie.php
Now for the forum rules.
As UMP is part of NFS Unlimited you are required to follow the rules posted in their general discussion forum, found here: http://forum.nfsunlimited.net/viewtopic.php?t=10
Along with those rules please do not post links to videos. There are plenty of places for you to spam random videos. UMP deals with RACING GAMES and nothing else. If you are interested in real racing videos I would reccomend you visit http://www.tremek.com - Any threads with links to videos, or videos that you are trying to submit will be automatically deleted and you will be sent a private message with a warning. If this persists, you will be removed from our forums and most likely banned from the NFS Unlimited forums.
Please feel free to post about anything that relates to racing game movies. What you are currently working on, help you need, etc. NFS Unlimited does provide several other forums for off-topic discussion as well as general discussion pretaining to Need For Speed. Topics will be moved there if they are not dealing with things that relate to UMP.
I only say this for the sake of saying it, I don't forsee any problems with anyone. I feel all important saying all that like I'm gonna crack a whip or bust a cap or something similar, Hahah
Have fun!