I've held lan-ish parties, where one group of people (5 or 6) are at one house (All my friends have bigger houses), and another half dozen connect via internet. Of course, the people on line get bored quickly and leave after a bit, but meh, you got your half dozen. I haven't had one in like three months, but I still have Ethernet splitters, and a stuff load of cords.
I'd suggest large amounts of drinks, get lots of zip strips (And duck tape), and don't forget do it in a place no one can hear you. It can get fairly loud. (Also, if you think you've got intelligent enough guys, wiring supplies. Nothing better then some guy in the back use a half dozen lamps to make his computer's inside impossibly light.
Also, at one I got everyone to play blockland via a LAN server. It was fun, we built a giant dong ship :D Which was promptly lost after I hit the power switch on my power strip, and we went back to play random games. (Kinda disorganized :D. However, we mostly played WoW, which I dislike. Sometimes we go on an xBox and play call of duty.)