Alot of folks have been using the Bubble Magus skimmers on smaller tanks with great results. I have never used one, but have seen them and they seem to be of very good quality. I have a 65 gallon I am getting ready to set back up and I am going to get the NAC6 for it. For $155, I don't think you can beat it.
Marinesolutionsinc sells them, that is where I am getting mine from.