My favorite place to rent is Aperturent.com. They're a local Atlanta company but they ship all over through FedEx, and their prices are great! They have Canon, Nikon, and Four-Thirds camera bodies and lenses as well as lighting gear and accessories. (Don't forget to rent a filter with that lens! I never shoot without a filter to protect the glass.) If you live in Atlanta, you can choose just a 3-day rental and pick up your rental equipment in person. That means NO SHIPPING costs. Their other rental rates are very competitive.
If you reserve or rent a lens and use the code 4JULY by July 4, 2010, you'll get 15% off the rental! Please use my referral link http://aperturent.com/r/226 to enter the site. They have an awesome referral program, and I'd love to help grow their business. Plus, their equipment is awesome.
One of my favorite lenses to rent, a Nikkor 24-70mm f/2.8G AF-S
From a shoot with the above lens.