I've never used this, and it's incredibly shady considering the users probably do not realize that their Hola browser plugin does this, but Hola runs a paid VPN service where you can get thousands of low-bandwidth connections on unique residential IP addresses, provided generously through their "free" VPN users.... It's essentially a legitimate attempt at running a botnet as a service.

But if the end justifies the means... http://luminati.io/