Hello,
assuming that you are looking for analog/asynchronous (and not ISDN) connectivity, you might want to think about a 2811 router with an NM-32A network module, or 2 NM-16A/S modules. There are various limitations and specifications for the different modules available, have a look at the link below for details.
The 2800 series is currently the latest (and therefore most expensive) Cisco product line. You could also look at the 2600XM router, together with the modules named above.
Serial Connectivity Network Modules
http://www.cisco.com/en/US/products/hw/routers/ps274/products_data_sheet09186a0080091b8b.html
HTH,
GP