You're probably gonna have to do at least a little bit of the work, here. Your '08 can take wheels in 15", 16", 17", 18"...all the way up to some keeerazy 24" chromies w/dubs. You can also choose between alloys and steelies...kinda depends what you're gonna do with your Jeep.
Literally hundreds and hundreds of choices.
Another messy complication: Are you just looking at getting new wheels, or wheels and tires? If both, then you wanna think about wheels with 4.5" backspacing or less, so there's no chance of rubbing your air dam, steering stops, fenders and, if you ever decide to get a lift, your aftermarket sway bar links.
I'd recommend you read the link below. Sounds like it's all about tires, but it deals with rims on unlifted Jeeps, as well.
Largest tire on stock JK? Here's your answer!
And here are some places to start looking at wheels. You want wheels with bolt pattern 5x5 (also called 5x127 on some sites).
Off Road Tires - Super Swampers, Pro Comp & Dick Cepek Tires, Mickey Thompson Wheels, KMC & XD Series Wheels - ATV Tire Package
Discount Tire, Custom Wheels, Truck & Car Rims | Discount Tire
Tire Rack - Your performance experts for tires and wheels
If you find something you dig, check with DTD (Discount Tire Direct), here on the forum. Not only will they price match, but their price is shipped to your door, whether you get just wheels, wheels & tires mounted, etc.
Good luck, and welcome to WF.