Belkin actually makes a number of compact, white USB hubs that are quite inconspicuous and would look good beside an iMac... but I have a caveat. I have one of these:
http://www.buy.com/retail/Product.a...78617&Type=PE&Category=Comp&Gad=0&dcaid=15894
Which is very similar to the newer ones except it's translucent dark grey (looked better with my G4 tower) that I grabbed for cheap at Staples. It's got all the features--4 ports, powered, status lights, and all the wires go out the back, so you don't have any clutter in the front of your desk.
And I despise the thing--it is CONSTANTLY "forgetting" to wake up with the computer. Basically, at random intervals after the computer sleeps (which puts it to sleep as well, no problem there), it will fail to kick back in. Only way to jumpstart it is to unplug and re-plug the power cord.
Maybe I just had a bum one, but it really put me off of Belkin--I had a cheesy, dirt-cheap silver hub from Radio Shack that worked absolutely perfectly in the same situation, nary a problem for two years.