I certainly wouldn't spend the money on aol--in most markets you can get minimal dsl for what it costs these days. I used access4less.net for a couple of years--$6 a month, much better at maintaining a connection than aol ever was. Their mail server would go down a day or two a month, though. Still, for the price--no ads, no special software, just a number that always connected, it was fine.
Any cheap isp that's reliable and doesn't put ads in your mail is fine. All you need is the connection--the mac will have everything else you need, so it doesn't matter if the isp "doesn't support macs."