Channel banks are still the cheapest way to get a lot of POTS lines out of an asterisk system.

Rotary: I use the zhone channel banks that I buy from a liquidator in texas. They are the Z-Plex 10b's. All I use them for is 24-ports of FXS that I then pass out for fax machines, cordless phones, door phones, SLT, etc etc. Caller ID works as well as all the other regular suspects.