Not really too much in the way of advice, although 3 random points:
1. Javascript/ajax won't work on most mobile device browsers
2. Mobile url's are generally a subdomain. ie/ make a simplified version of your site at: m.domain.com or mobile.domain.com
3. Most smartphones now are getting better displaying full pages rather than simplified ones, wap look-a-likes (apart from my point 1). The iPhone or new blackberries render the page in a way that keeps the layout the same as on a full screen.
Good luck, I'm interested in this and hope others can contibute something a bit more informed than me!