Another forum I go on organises a yearly dinner (well, multiple, one for each city) for Christmas. It's a great opportunity for people to get together face to face. We already do a lot of that, but there's also a lot of forum members who we haven't met yet!
November or early December seems to be the best time to organise these things to avoid people being busy with family xmas parties.
The Titanium Bar has some Christmas function packages which are worth a look.
Dinner I think is a bit much, $60 per person, 4 course set meal. The other packages are ****tail parties.
I've been doing some maths on it. Assuming we get 50 people along, we could get 6 platters of food (meant to cater for 8-10 each) and a $500 bar tab for about $15 per person. Admittedly that only works out to be about 1-2 drinks per person, but it gets you started and fed, and we could probably up it quite a bit.
Anyhow, if you're interested let me know. We'll need definite numbers and payment up front.