I run a couple of Macs, and I recently chose Pipex for my broadband and absolutely no complaints.
They provide a Speedtouch USB modem and a couple of filters as part of the package. I will probably change to a wireless router soon but the present set up works fine. I initially had a bit of trouble setting it all up (it was finger trouble on my part!) but their tech. dept. were very helpful.
Be wary of Tiscali who will tell you after a couple of pages of signing in that they don't support Macs!
Otherwise I think Daysleeper has pretty much covered it.
Hope this helps.