DummyMac is a bandwidth manager. You can limit inbound/outbound bandwidth choosing a port range. Very useful for dialup connections.
throttled is a bandwidth shaping application for Mac OS X and FreeBSD which allows you to cap your upstream bandwidth, prioritize ACK packets, and keep your download speeds high even when your server is sending out at full speed.
(shareware) Throttled Pro optimizes your internet connection and provides "QoS (Quality of Service)". Features include: Provides instantaneous response for SSH, HTTP, HTTPS, POP, IMAP and VNC connections. Also allows you to prioritize any other internet protocol you want to remain responsive under heavy load. Includes optimizations for many online games including Unreal Tournament 2004, World of Warcraft, Call of Duty, Ghost Recon, Starcraft, Warcraft II, Warcraft III, and Diablo II. Manages BitTorrent, FTP, DCC and other file sharing protocols so your connection always stays lag free.
Throttled switch is an easy way to lauch and stop the throttled process.