How can I make bandwidth intensive applications have lower priority than other apps like web browsing/skype

Solution 1:

There are some routers that can handle this. I think D-Link refers to this feature as 'GameFuel', and the pre-sets prioritize one-line game traffic over others, but you can always adjust the settings. D-Link seems to have a set of 'Gaming' routers (like the 108G) that contain this feature.

By putting the feature into your local network router, I think you'll have the best experience, once you figure out the appropriate ports to prioritize (or de-prioritize).

Caveat: I haven't actually done this, I'm just saying that it appears to be possible with this equipment.