I love creating mobile-friendly themes for Drupal 7 using the Sky and the Adaptive Theme. It looks great out of the box and is fully responsive including nice styling for your mobile menus. I looked into using the Omega theme which is quite popular. I found that there was a lot of documentation to read. I was looking for a quick way to build a mobile-friendly theme for a volunteer project for my brother’s construction business. So I turned to Sky and Adaptive Theme. (http://drupal.org/project/sky)
I like the Sky theme for several reasons. It looks great out of the box and is mobile ready. Choose your color scheme and voila! It looks great in all of the different mobile widths. Version 3.x hides the wide menu buttons by default and you on the menu icon to see the menu items. This is rapidly becoming standard for mobile designs. Many users will be familiar with this way of displaying menus from using web apps.Be sure to download and install the Adpative theme first. (http://drupal.org/project/adaptivetheme) This is the parent theme for Sky. Follow the directions to effectively sub-theme Sky and create your own custom mobile-friendly theme. Use the subtheme called Footheme to make a sub-theme using one of Adaptive Themes. Due to the complexity of sub-theming these colorable themes they built this easy to configure starter themes which can get you up and sub-theming very quickly. (http://drupal.org/project/footheme).
Contact Katy for help with your own custom Drupal 7 theme that is mobile-friendly.