I wrote a simple script last week that sends email alerts when you have new twitter mentions. The script simply searches your @username every five minutes, or whatever interval you choose, and sends an email if a new mention is found.
If you want to try it, click here to download the zip file.
Instructions: This script requires PHP 5 and the ability to setup cron jobs.
Set the values in the config section of the twitter.php file. Upload the file somewhere where your server can execute PHP. Set a cron job to run this script however often you would like to check for new mentions. Ask your host for help setting up a cron job.
You should follow me on Twitter here.


