I like the EK Success Curvy Cutter system, which has several other shape templates available as well, such as ovals and rounded squares. It cuts in twelve different sizes per template, although not quite as large as you're looking for.
I'm sure someone will tell you to just get a Cricut, but I get the impression you're looking for a lower-budget tool, which is also fine.
I use the EK Success- Cutter Bee. Maybe it's just me, but it takes a certain knack to get it right everytime. I haven't made circles in a while, but I just got SCAL2 for my Expression-- I'm pretty sure they'll be circles for that. I'm hoping to make bigger ones with it.
I also love raiding the kitchen for tools, as they said you can get some of the best sizes for a great price! Whenever we lose a lid or the bottom for a piece of tupperware the lone piece gets carried away to my scrap room. I also have a scratched CD I use for medium and small circles. I also hunted down a roughly 10.5" plate at the thrift store that now has a permanent home in my scrap room.
I love my Fiskars Ultra Shape Express, with the large template circles. The advantage is that you lay the circles right over the paper. What you see is what you cut. No guessing! The trick is to hold the USX like a computer mouse, and make sure that the template is right side up (the Fiskars name should be face-up). Easy peasy.
I bought one of those Compasses like you use in school to draw a circle. One side is the pencil and one is a pointed metal thingy that you place on the paper and then turn the pencil around in a circle. (I tend to go for inexpensive solutions.)
I must admit that a Cricut Expression is on my wish list though.