We have five dedicated test computers at work. We also have 4 iPads, an android tablet and a playbook. We have an apple touch to test for mobile, and several people on the team have android phones. Unfortunately we're running out of space as our team expands so we're going to be ditching the computers and getting Browserstack. Depending on what city you're in there are device labs that are open to the public so that you can test on different devices. http://opendevicelab.com/.

I've only used Browserstack, but I'm a big fan. Also awesome since it support my local dev environment very easily.