I am thin and in decent shape. However, I don't have a lot of muscle definition and am fairly new to fitness. My problem is that I have cellulite on my butt and thighs. Are there any exercises you could recommend? Thanks!

You are what is called "skinny fat", meaning while not overweight, you probably have a higher body fat percentage.

Getting into a good diet and exercise routine (check all the stickies at the top of the forums) will most likely help to build more muscle (no, you won't get all freaky big), and reduce some fat.

Doing some of the bigger compound lifts, like squats, lunges, deadlifts, will help to shape the legs. Nothing you can do will specifically reduce the fat from your legs (or anywhere else) though - only as a whole.

In a nutshell - work your body as a whole to burn fat and build some muscle, you most likely will lose some of the cellulite, but maybe not all of it, there is no way of knowing or controlling that. Also, don't mess with any of the cellulite creams and gimmicks either - if any of them actually worked, we would be a world free of cellulite.