TweetGT is a project mainly written in PHP, it's free.
Tweets: Geotagged
TweetGT - Tweets: Geotagged
This is a simple Zend Framework project that allows you to post a geotagged tweet. A working implementation is available at http://tweetgt.funkymongoose.com.
It uses Twitter's OAuth authentication system (via Zend_Oauth_Consumer) so that you don't need to give the application your login details.