I will say that the plan I made for doing this club is long, please give your thoughts on my year plan and the prizes I'm planning on giving out, thank you for rewarding in advance.

Lesson plan term 1 computer club:
1 introduction + what we will do 

2 game maker basic game + home work to make a more complex game with game maker, packet of sweets as a prize

3 operating system introduction, talking about stuff it does + suse studio competition with prize

4- web pages with HTML and CSS
+ prize for best web page

5- something of the people's choice to expand upon + deciding what to do next term out of the above subjects.

Terms in no order
- writing a t engine module for a roguelike for one side and a basic java game for the other, the top 2 winners from these get a cheap pc game from game

- fully fledged website with php etc. prize is perhaps some network software for servers and a few flash games for the site on a DVD

- learning operating systems, one use python and the other uses ruby Winners gets a DVD with Ubuntu studio 13.04 big version burned on for python and ruby gets Debian plus a load of cool software and games

- the last term larger emphasis on one of the above, people get a chance to learn from their mistakes and make something amazing, winner will win 3 for 10 pound games from game, a 2gb sd card and £5 voucher . And if game will upload onto source forge.net 

What age group is the club for ?

-I run a lunchtime school tech club (high school- KS3) and I found MIT's Scratch was really good for getting the kids involved in development.
Gamemaker I did not have so much success with as the students found it a bit fiddly, but i'm in no ways saying don't try it just make sure you are aware of the alternatives.

-I think teaching about OS's would probably have to be for an older age group I would not do this for anyone 16 or under, same with PHP development.

-Really like the prizes you have chosen, may have to use some of those for my club :-)

Just note the type of students,their interest and participation will vary greatly from school to school, this is just my opinion based on the type of students I have. I would be very interested in hearing how it goes.

I'd love to hear suggestions, cause I have tech club at my own highschool, and frankly, it's pretty much dead for the moment, mainly cause most people don't really have much of an interest in tech....

EDIT:
I also run during lunch time as well...

Try giving them an objective, I don't know about your location but in the UK Manchester Uni run an annual competition in animation so I got my club to focus on that, it doesn't hurt that they had some pretty amazing prizes (£500 vouchers, Laptops etc) so some students were sold on that.

I'm a big advocate of Scratch, Ive done some stuff with Alice as well- A big part is letting them see whats possible (Find demos or make your own) hopefully that will provide some inspiration.