WordPress "Must-Use" Tutorials
WordPress multisite how to - making sense of the network feature from what was wordpress mu
If you are interested in keeping up with how the merge of WordPress & WordPress MU is progressing here is a list of resources that you can follow:
Let the fun begin 
Includes 3 ebooks with plugins -
Network Home Pages: aggregate global content, set up sitewide tags, create a huge tags cloud like the one seen on WordPress.com, global footers and menus, setting defaults & more
Custom Registration: sign up on sub sites, multilingual signup pages, stop spam blogs
WP Curator: pick and choose posts from sub sites to feature on the main home page of your network
Network Home Pages, Custom Registration & WP Curator – $35.90 for all three. Purchase
Awesome twitter list, thanks!