Both my solo project bandcamp and soundcloud link to a project with a friend are in my signature.
Soundcloud is nice for it's community feature, though I don't utilize it really, just nice to know it has a way of connecting with like-minded people. Bandcamp is good for it's promotional factor and the fact that you can charge money of any amount for your music. I personally use soundcloud way more, especially since I have it on my phone and can make low quality field recordings at will, which I can later download on an actual computer and use in my tracks. Handy little thing.