MMiThemer got updated. The new version fixes some compatibility issues with firmware 1.1.4. I’ve tried the new version and the downloaded themes now show in both Summerboard and Customize. Please check my full review for more information.
» MMiThemer 0.21beta – Theme switcher for your iPhone

MMiThemer is a very handy app from the guys of ModMyIfone.com. MMiThemer let’s you download and install hundreds of summerboard themes directly from within the application. The app works much like Customize, you can browse and preview the themes before actually installing them.
» MMiThemer – Theme switcher for your iPhone