Well I've been fooling around the with pktgen module that comes with Linux 2.6. For those who don't know about it, you can read up on it in your Kernel Source's Documentation/net/pktgen.txt. The generator is designed for network stress testing, and they try to squeeze the most performance out of it by making it a module and using only userland tools to handle the packet creation. It has some interesting features, like filling each packet with garbage data that it randomly generates. Sending 200,000 TCP/80 hits generating new packets every 5,000 gives you a good idea as to how much traffic your server can handle before it dies. This C/400 I was testing lasted 8 seconds. One thing I did notice, if you don't have certain other kernel options checked (fast packet queuing, or whatever it is called), your network stack will fill up and you will have to bring the interface down and back up.
Of course, "out in the wilds" this wouldn't be able to do much harm as your bandwidth would be limited, however on a lan this could be a fun toy to play with. Anyone else had any luck/fun/worthwhile and interesting phenomenon they've observed while running this?