Looking for a cheap or free WaterMark program

I'm new to Mac, I use to run a Dell for many years..
I must say now that I've gone Mac, I'll never go back! ;D

Anyways on my Dell I had PhotoShop CS & use to waterMark all my pics before ever posting any of them of line.
Trust me I take LOTS of Pic's.

Anyways I dont wanna spend the $200.00 to buy the Aperture software.
& was hoping you guys could help me find a much cheaper way or maybe even a free way to watermark all my pictures..

I take lots of off road race pictures & such & love to post them on line.
I dont do it for money, Its just my hobby.

Anyways I plan to visit a big race next month & would like to get myself all set up before I go.

FYI, I'm running the latest MacBook Pro 15", I bought it about 5-6 months ago, So I need a program that will work with my software.. ( Or would that be Hardware? )

I think its version 10.5.8
I would never of even known this but this site makes you enter a Prefix?
& so I looked up my "About this Mac"

Imagewell will do this perfectly, and it's great app with lots of extra features.
There is a free trial period and then it $20 for the licence, which is well worth it.
You can download it here:

ImageWell 3.5.3 software download - Mac OS X - VersionTracker