Since I have to do a lot of YouTube uploads as part of my volunteer work, my Internet connection was getting choked causing problem for other work (email, ftp, etc.). Thanks to Mac OS X built-in ipfw I can limit uplink connection based on services, destination ports or IPs! This is just a quick test to limit the uplink for web uploads to 200KB/sec.
ipfw pipe 10 config bw 200KByte/s ipfw queue 75 config pipe 10 weight 75 ipfw add 100 queue 75 ip from me to any dst-port 80,443
Help taken from Destructive Thinking.