Last.fm is for you! Identified as one of the most popular online music communities.
Last.fm offers a lot of features that include personalized radio stations, tagging, scrobbling (streaming & iPod capability), wikiing, and listings of musical events. Their latest addition are widgets and they can be embedded into your blog, personal webpage, Facebook or MySpace page.
Users can create profiles where you share your listening history, post events on an online calendar, keep an online journal, add friends, and add groups (people with similar musical tastes).