Business 2.0 published an article which provides a roundup of thoughts circulating around the Mac Web and came up with their own "What's Next for Apple?" predictions.
From most likely to least, they provide speculation on the following products:
Wireless iPod
vPod (Video iPod)
iHome (Media Center)
iPod on Wheels (Enhanced iPod/Car interaction)
iPhone (Apple Branded)
A photo essay provides some visuals on these expected products.
Much of the thinking is based on analyst thoughts as well as circulating rumors and patents. Of note, a few of the items have been publicly rejected from comments by Steve Jobs in the past. Specifically, the idea of Apple branded Phones and TV/Computer integration have been denied in the past.
Jobs also expressed doubts about the sucess of portable video players, but didn't deny that they weren't working on such items in their labs.