Official Twitter app for Nokia S40 devices available at Nokia Store
Twitter app for Nokia S40 devices is ready to be downloaded from Nokia Store. The app looks fairly beautiful, identical to iPhone app with tabbed parts containing : Timeline, Mentions, Connect, Me, and Compose.
S40 also runs java apps, so it must not be too much pain to make the app work on S40 devices. S40 devices may not be much popular in Europian countries, but it has alot users in India.