I've heard great things about taking a 5 gallon bucket, getting a cheap-o fan and cutting a hole in the top of the bucket lid and mount the fan blowing down into it. Then you put some holes down towards the bottom 3rd of the bucket to vent out (or in if you prefer, with fan flipped the other way) then putting your ona gel/water/watev mix in the bottom of the bucket. I will be building one of these soon and will post my results. =)