Over at Diary of a Mobile Addict, Mordy has a great write up of the various ways you can trick a Pocket PC app into running on a Windows Mobile Smartphone. It starts out with the first thing you should do: just try installing it because it might work. From there, the article moves on to tips for yanking the binaries out of the .cab, setting up a Pocket PC emulator as a staging area for the install, and using an application that will let you send screen taps for Pocket PC apps that demand it. Unfortunately, this won’t work perfectly for landscape QVGA devices like the Q, Dash, or Blackjack. –Link

Update: Mordy wrote to point out that landscape QVGA devices should work fine with this approach in many cases, but some applications may have problems with it.