If you happen to use MS Word 2007 for equations and wonders why the heck there isn't a shortcut to subscript and superscript then you will like what I just found couple of minutes ago.
If you want to type e1 with 1 as subscript just type e_1. The moment you hit space it will become what you want. To make 1 superscript type e^1 and space. Enjoy!