A good example is Cisco WAAS, a cool video showing how it works is here: http://www.cisco.com/cdc_content_elements/flash/ans/index.html
See here for data sheets and specs: http://www.cisco.com/en/US/products/ps5680/Products_Sub_Category_Home.html
Cisco's solution is inexpensive and you can use your existing router investment to do all the heavy lifting.
"Ask not what A Group of Employees can do for you. But ask what can All Employees do for A Group of Employees." -- Mike Dennison