Soundcloud:

Features:  If you’re already a Soundcloud user and/or want to support the artists by listening, check out Soundcloud where you’ll find both mixes and original tracks:  Listen and/or download.

Mixcloud:

Features:  If you’re already a Mixcloud user and/or want to support the artists by listening, check out Mixcloud.  Tracklist information is displayed “real time” while listening.  Only mixes are allowed, not tracks.  Listen only, downloads are not supported.