Bandwidth Monitor NG is a small and console-based live network and disk-io bandwidth monitor for Linux, BSD, Solaris, Mac OS X and others. features: output of KB/s, Kb/s, packets, errors, average, max and total sum; in curses, plain console, CSV or HTML
MOVED TO:
https://github.com/vgropp/bwm-ng
Sload is a console/terminal application which monitors network interface load of the remote device (by SNMP) in real time.
Bandwidth Monitoring Tools For Linux
(Requires Python 2.4 or later)
UPDATE: good known alternative is "ifstat"
http://gael.roualland.free.fr/ifstat/
Example of use:
ifstat -b -i "FastEthernet0/19" -s public@172.18.216.1
It's possible to monitor multiple interfaces in the same time !
An easy-to-configure bandwidth monitor and grapher, but so much more. Cross-platform, simpler alternative to MRTG and CACTII. Graph any numeric data you can get from SNMP or an XML (and HTML) source (local or http/https/ftp). Windows and Linux.