My predictions for the interesting items of the Stevenote (i.e. ignoring jokes about Vista and self-congratulatory bloviating about iPod sales, iTunes downloads, switchers, retail stores and market-share growth)
1) Announcement of new iPhone: 3G and new software for sure, maybe GPS (but only if it'll actually work well), available world-wide in July.
2) Lots of discussion of the cool things you can do with this phone, with emphasis on the SDK and the iTunes app store. Probably demo of some cool Apple.app that integrates your iPhone, your Mac's at home and at work, and the new Apple web/cloud service:
3) Announcement of Apple.Me or whatever they're calling the new version of .Mac. Major upgrades of Apple's online service... more storage, faster, push-email, etc. possibly a suite of network apps, and if so, I'd expect them to be derivations of Googles done in partnership with Google.
4) Tantalizing hints about OS X 10.6
5) One more thing: new hardware (probably an updated MacPro, and or MacMini, but I remain ever hopeful that Apple will one day release an xMac).