Does anyone know if this is possible, or better yet, how to do it....

Let's say I have 2 seperate DSL or Cable connections.
Is it possible to use both at the same time on one computer? In other words - I wanna soak up bandwidth from both connections at the same time on one machine. (Evil grin).
I've seen in the past where you could take 2 dialup connections and 'bridge' them somehow on one machine...if I remember right - it used one connection for upstream and the other one for downstream. Anyway I wanna do something similar with 2 broadband connections.
Any suggestions, ideas, pointers welcome...
Thanks!