Cisco AS2511-RJ works pretty well. I grew particularly fond of being able to do 'telnet toaster.console'.. the only thing that it lacks, imo, is scrollback.
Surely you mean "telnet toaster.console 20XX" where XX is the line number of the async port. I would live to be able to do VIPs for each port but AFAIK there isn't a way unless you know different. ATM we have to put a motd on the 2621 which lists which port is which. So a typical session is: telnet serial.london [read motd to find which port number you're after] exit telnet serial.london 20XX