In an attempt to create some "realistic" clothing, I used Shrinkwrap to project a mesh onto a character. So that the clothing appears elastic, and not glued to the them, I then used Convex Hull on the horizontal loops (I tried it on the entire mesh but it had unwanted results). Unfortunately it has left me with LOTS of internal geometry (see image), and was just wondering if there was a way to delete it all. I thought I remembered reading about such an operation in the Blender manual, but can't seem to find it again.
One way is to select bottom most and top most rim (edge loop) and make them seams. Then switch to face select, select one of external faces on the body and CTRL+L to select linked (it won't work in edge or vertex select modes). This way you will have selected only external geometry. Then you can press CTRL+I to reverse selection and delete faces. It won't work though if inner geometry is linked somewhere else then on top and bottom with external geometry. If that's the case, the best way would be select face loops one by one with ALT+SHIFT+right click. After all external faces would be selected, CTRL+I and delete.
You can try to go in top ortho view (7 for top, 5 for ortho/perspective), set the selection mode to Edge (in edit mode Ctrl+Tab, then select Edge, then use the circular selection tool with C. You can use the mouse wheel to change the size of the circle. When your done, hit Enter, then X and select "edges".