Traffic Shaping, Failover tools

I have just become the only IT manager of a small business. We have multiple internet providers (Comcast, Time Warner, XO and Qwest).

I'm looking for some solutions that can aggregate those connections, and use traffic shaping to provide the best route.

What are some of my options? Free? Low cost?

I don't mind using a linux based system either.

Just need some options.

Suggestions for a combined system.

• The cache and other things: Squid and the accelerator mode (at the Squid Cache Wiki)
• Content filtering: SquidGuard (there is also DansGuardian)
• Tracking things: MRTG
• And, maybe Netmon too

Some more reading on Squid load balancing at the Sun site.
Squid for balancing connections over multiple links.

And, You should take this question to serverfault