Here are couple of nice links to get mp3s of baile funk:
Funk Neurótico is a pretty famous site, where you can get proibidão songs as well as other stuff. The good thing is: There is plenty of stuff available for download and they put more on the site every week. There's a lot to go through and since you can listen before downloading, it can be frustrating shooting in the dark. The quality is also always 128kps so it's nothing to dj with... Also every song ends on a vinheta (= a radio hook) advertising the site and it's pretty annoying. Anyhow, loads of stuff there, browse through! (From the main site you choose músicas and then either atuais, rap's, melody's or montagens) And don't forget to peep through the video section...
Another one lesser known is DJ's club, which is aimed mainly for the producers. Here you'll be able to find songs from some of the top DJs in the produções section. But what's more important there's loops and samples and instrumentals for producing baile funk. Some of them are in wav, but others in 128kps mp3s and since you can't tell before you've downloaded them, it can be pretty frustrating going them through. Once I've browsed more I'll let you know which one's are in wav and worth while. If you find some, please leave a comment and I'll link them on the blog. Besides the loops and a capelas that everybody understands, browse through also the pontos (=sample-loops taken from other songs) and viradas (=the "turnings" which is more or less like a break or a bridge). Bases means instrumentals.