I know for a fact it supports SNMP - it's in the Airport Utility. And it's apparently how the Airport Utility communicates with the base station.

The snmpwalk did in fact produce a crapload of output, including a list of all the devices using the base station's DHCP.

Last night I tried to install MRTG using MacPorts but I didn't get anywhere. It was taking hours to download all the bits and pieces needed to compile MRTG and it seems to just get stuck at some point on one piece without ever getting to the actual MRTG source. Unfortunately I haven't been able to find a binary for Mac OS. Why do these guys assume everyone likes to compile this stuff? I can't be the only one who thinks having binaries for Mac OS, Win32, etc. would be useful, if not just convenient.

I'll try that Byte-o-Meter today. But this might all be moot if I use the WRT54GL as a QoS gateway with the VOIP box connected directly to it. In that case I'll use the WRT's bandwidth monitor because it will include all the voip traffic as well.