There are many Twitter applications available for smartphones and PDAs. Given I still run Windows Mobile 5 (WM5) with my HP iPAQ HW6965 mobile, it's a bit tricker to find a good solution as most new releases focus on iPhone, BlackBerry and WM6.
  • TinyTwitter: fast, simple, complete but one account only. No URL shortening, only TwitPic support. Shows timeline cache without reload need.
  • Twikini: Multi-account & URL shortening. Fast loading. Timeline requires update upon program start. Accounts switch forces timeline loading.
  • PockeTwit: Best looking with "slide effects". Multi-account, build-in cam. Think "TweetDeck for WM". No own timeline per account, all mixed.
Twitter on WM5 conclusion (for now): I will keep TinyTwitter for my own account (single) and for multiple other accounts to manage: Twikini.