This is where it gets a bit interesting- the film releases seem to be fairly well split across the scene proper and p2p groups as of the last couple of years more so that just about any other aspect of releases (the only thing to come close is probably the 360 but that is still worlds apart).
I have no great love for the p2p groups but those that know what they are doing can usually pull it off quite well- the scene tends to do it well (outside of cams and r5 releases at least) and be pulled up and fixed if not but they are limited by the scene rules as their suggested limits/standards are often right on the bubble when it comes to quality (this is especially evident in TV shows):
http://pix.gbatemp.net/32303/The.XviD.Rele...ndards.2009.png (not sure if there are any new standards being put forward at the moment).
Naturally p2p is a very fractured environment with it having no rules and no real central hub (torrents, usenet, file storage sites (not to mention the hundreds of different options here and passworded BS), ftp, irc groups (not sure of the current state but many anime groups went this way), other p2p methods based on gnutella or versions thereof so as hinted at can go either way- a nice 1 gig H264 encode (nothing close to this available for scene type releases) will trounce even a well made 1 gig xvid encode for your standard film (it is easy enough to generate examples to go either way but in the wild it generally makes life easier) but on the flipside some of the stuff p2p groups is trash (occasionally the only way to get some of the less common stuff and even some TV shows at least until repeats air but still trash). Equally some of the p2p groups (especially in the R5 scene) are very very quick and often beat the scene to the punch. Similarly p2p groups can release what they like when they like so it can be easier in some methods to track down older films and if they make new releases the advancements in encoding methods over the last couple of years can really show.
To this end there are still scene pre databases
http://www.orlydb.com/s/xvid and some of the old staples of the xvid scene now have some measure of p2p release listing as well
http://www.vcdq.com/browse/1/0/0/9/0/0/0/0/0/0 (bonus points- many greasemonkey scripts are available to hook IMDB into to VCDQ- got an IMDB url, got the name of the scene release one click later).
Mods- I think those two sites should be OK (they have certainly be linked around here several times) but if not lose them.
Others- double standard on several levels sure but it is often considered quite bad form to use scene release names for things other than games (even them some PC games are a bit of a touchy subject) around here.