Anyone out there use a special brush to clean their rims? I'm looking for something that will reach the "backside" of the rim - that grime and dirt that I can't get to is annoying me...

I have a small collection. Here are my favoirites:
One (http://www.autogeek.net/meguiars-wheel-brush.html)
Two (http://www.autogeek.net/oxospwhbr.html)
Three (http://www.griotsgarage.com/catalog.jsp?L1=L1_1000&L2=L2_1002&SKU=15220)

I use number one and three the most. One can be found at WalMart.

I also have three favorites for the outside of wheels :-D

If your wheels are filthy, use this (http://www.eagleone.com/pages/products/product.asp?itemid=1003&cat=5006).

Be careful with the Meq brush as it can really fling liquid at you as the bristles flex. You don't want any wheel cleaner in your eye!

Save yourself a bunch of trouble and just remove the wheels if you want to clean the back sides. I rotate my tires every 5K miles, and I use this opportunity to give each wheel a thorough cleaning. Apply a coat of wax at the same time and they'll clean easily. The real problem is neglect - make time to wash your wheels at least monthly and you won't have such a big job to do or risk damaging the wheel finish.

hmmm... don't imagine I'm going to remove the E's wheels every time I wash it though. would it be any easier to just jack it up?

You can also use a cheap baby bottle brush to reach the interior portion or the wheels.
They make some of them out of sponge material so you don't have
to worry about scratching the finish.