A quick post to mention that a few native Symbian S60 Twitter clients are under development. I haven't installed or tried any of these, but when I have the time, I'll post my feedback here.
Gravity will be a commercial product, developed by mobileways, who already offer native S60 Twitter functionality within their WirelessIRC software. From some of the early reviews of the beta, Gravity looks like it will offer a fairly complete Twitter solution, comparable to many desktop clients.
[Update] Gravity has now been released,costs $10 (about £7), and a demo version is available to download. I played with the demo for about half an hour and knew right away that this is the best Twitter client out there for Symbian devices. So I bought it. I'll probably do a full review of it soon, after I've been using it for a few days. In the meantime, if you're a serious Twitter user, and have a S60 device (like a Nokia E71, N95, N96 etc) definitely give the demo a whirl on your device.
I Am Doing
TwitS60 is an open source project, which claims to be under active development. There's nothing to download at the time of writing, so one to bookmark and check every now and then to see if it will be any good.
If readers know of any other non-Java Twitter clients for S60, feel free to let me know via a comment on this post.