Resharper is definitely a great tool. It has a moderate learning curve but is easy to pick up for some simple things and add mastery later. It is a good price for students and kinda expensive for the rest of us. Resharper is similar to CodeRush, but seems to have a larger following.
PowerCommands is a great set of add-ons that comes free from Microsoft. Things like "Open in Windows Explorer", "Command Prompt Here", and Copy/Paste references.
A discussion regarding add-ins is floating around here somewhere.
For straight-up customization, changing colors is fun, easy, and gives you a big bang for your buck. I prefer a slightly personalized version of Rob Conery's TextMate theme for Visual Studio. Once you get colors you like, you can just export the settings and carry them with you wherever you go.
Related to colors and themes, the Consolas font pack is pretty nifty and easy on the eye.
And like John recommends, a mastery of keyboard shortcuts will pay big dividends.