I also use AIM to run my Monday night games. In addition, I have found Microsoft Excel to be invaluable for combats...it even has the coordinate system built in. (Select all, make the cells 17 pixels wide...perfect grid).
The AIM dice roller, however, tends to be a bit buggy in my experience. Two people roll dice within...5 or 6 seconds of each other, they tend to get the same result. My experience says this happens about 85% of the time, so you may want to find some other method of die rolling.