I'm looking for an inexpensive wide angle lense for my Nikon D5000?

I already own a 18-55 and a 55-200.

The least expensive good wide angle lenses are the Tokina 11-16mm DX2 (not the DX as it won't autofocus on your camera), or the Sigma 8-16mm

Your 18-55mm IS a wideangle lens, roughly equivalent to 28mm on 35mm format at the short end.

Nine times out of ten, if that isn't wide enough, you're doing something wrong.

18mm is wide angle and since you already have it, it's free.

http://keerok-photography.blogspot.com/2011/05/lenses-so-many-of-them-there-is-no-best.html

It's great isn't it. You ask for information on wide angle lenses and some muppet always has to chip in that the 18mm is wide enough. Sure, 18mm is technically wide angle, but it's nowhere near the view of a 10mm or 11mm ultra-wide. You wouldn't be asking if you weren't finding the 18mm restrictive!

The Sigma 10-20mm f4.5-5.6 HSM is the cheapest good very wide angle lens for your camera. Make sure you get the Nikon HSM version or it won't fit and auto-focus. It gets very good reviews. Amazon prices are usually pretty good for that lens.

The Sigma 8-16mm is the widest zoom on the market and the Tokina 11-16mm is probably the sharpest, but both are quite a bit more expensive. You have to be careful with the Tokina because there are a lot of older ones out there which won't auto-focus on the D5100. There's also a Tamron 10-24mm lens, but it is more expensive than the Sigma 10-20mm and not reputed to be as good.