Though there are now plenty of third party apps for this, Twitter has just launched a new mobile version of its website, optimised for iPhone, Android and N60.
I did try to use the old version of the mobile Twitter site before switching to Tweetie and Tweetdeck, and it wasn't the best user experience, and it was difficult to keep a track of mentions and direct messages.
According to the Twitter blog, plenty of people are still accessing Twitter via mobile browsers. I've been trying it out...
The look of the new mobile site is a big improvement on the previous version, and now matches the look of the desktop site:
Tweets are easier to read now, and most useful of all is the addition of tabs towards the top of the page so you can switch between mentions, direct messages etc.
Towards the foot of the page, you can see an update of your status, as well as the search box and current trending topics:
The new mobile site has incorporated many of the more useful features from apps like Tweetdeck, such as reply and retweet buttons, the tabs for viewing mentions and direct messages, though it is less useful as a monitoring tool than third party apps.
You can search for a selected keyword or phrase and see results, but you can't save these searches for repeated use, or add another column for this:
The new Twitter mobile site is a big improvement, and it is now much easier to use, but it still lacks some of the more useful features of Tweetie and Tweetdeck, so I can't see many users abandoning the third party clients.