Depends on what your local cable company offers. Here in RI Cox offers ESPNHD, HBOHD, INHD1, INHD2, DiscoveryHD, ShowtimeHD, and just recently the local NBC (which is actually not broadcast on the free airwaves yet).
I still use my $300 Motorola HDT100 O-T-A receiver and $60 Radio Shack attic antenna to get the digital HD broadcasts of ABC, CBS, NBC, PBS, WB, UPN, and Fox from Boston. Most of the good stuff (Law and Order, Alias, NFL football, etc) is on the networks and Cox's NBCHD is still 4:3 instead of 16:9.
I still use my $300 Motorola HDT100 O-T-A receiver and $60 Radio Shack attic antenna to get the digital HD broadcasts of ABC, CBS, NBC, PBS, WB, UPN, and Fox from Boston. Most of the good stuff (Law and Order, Alias, NFL football, etc) is on the networks and Cox's NBCHD is still 4:3 instead of 16:9.