For those who use Sibelius (and for the rest of you that should :)) they have created a Users Group that meets in Hollywood and will probably start more around the country.  If you are unfamiliar with users groups, they are hosted by the software company and hold monthly meetings with free tutorials, guest speakers, and raffle off some goodies.  Sibelius is also doing a nation-wide tour promoting version 4. 

The website for the Southern California group is here: http://groups.yahoo.com/group/scsug/

It's a good place to direct your notation questions too :)

This website has made my transition to Sibelius from Finale smoother than I could have possibly imagined.  I second Jesse's recommendation!

-------

Actually, the one I've been using is the ";sibelius-list"; group.  This one has a much more comprehensive and thorough collection of articles:

http://groups.yahoo.com/group/sibelius-list/

The only drawback to using this Yahoo groups system (unless someone knows of a way to changes the search options) is that out of the 23,000+ posts that have been made, each time you search it only searches the 1,000 most recent posts.  So, while many articles may be specific to different versions of Sibelius, a lot of articles would pertain to Sibelius 1-4.  Anyhow, these are both great resources.