Gamefest is probably the biggest game technology event on the Microsoft calendar. The 2007 conference hapened earlier this year (in the U.S, of course), and the presentations and some of the audio from speaker sessions have now been posted online for download. There's some very useful stuff here f you've been playing with XNA. The best thing is, the content's very 'accessible' - I've never been a games dev guy (I play games, and leave the hard part to the genii) and I can still understand alot of the slides.
I'd recommend checking theses slides out if you're interested in joining the Games Development category of Imagine Cup - some very useful, XNA / DirectX specific information there which could help you out with your entries quite a bit. I know there's also a number of lecturers wanting to begin teaching XNA - these materials would provide some good teaching references (in addition to the XNA curriculum that is available at the Academic Resource Centre.)
In other XNA news, Glenn Wilson has informed me that Dream Build Play will be starting up again soon. For those of you at the Melbourne Mix On Campus, the video that Glenn showed at the start of his demo were the finalist entries from 2007's Dream Build Play - the idea is essentially that a whole bunch of amateur/hobbyist games developers get together and build some fun stuff. I'll keep you posted with more details as they come in - Glenn is looking at get something nice from Australia included at Dream Build PLay in 2008, and will be looking for collaborators, so if you're interested, watch this space.
Glenn is also starting an XNA users group (it will be country wide). You can sign up for the group at www.virtualrealm.com.au. Joining user groups is a fun and easy way to share your knowledge with other but also to learn alot of stuff from other enthusiasts in your community. If you are serious about being a games developer, I'd sign up at Glenn's blog now - you really have nothing to lose.