i'm in an environmental club at school, it's pretty fun, but i want to ask yous guys for some ideas of projects to do that might actually make a difference

not looking for something huge, just anything that would benefit the environment

First thing that comes to mind, compost.

Yeah diffenately.

Create a collection container that you put aluminum cans in and then sell them off with the proceeds going to something/someone that is deserving.

Run Folding @ Home Software (http://folding.stanford.edu/) on computers running on idle to utilize them more.

Recycling, making sure the office recycles their ink cartridges, office paper, etc

Repair things so the school isn't buying new things.

Perhaps (where permissable), install a solar panel and bank of storage batteries. If you have a good science (electronics/physics) teacher and students they could do this. It could potentially light a classroom, occasionally at least, and also serve as a learning tool for classes - Would need fiancing and approval though

Designate a garden (if you have them...concrete jungle school?) and landscape it to have water/salt tolerant plants, thus proving you can have a nice garden that isn't water hungry.

If it doesn't have to be on school property, check with your city to see if there is a vacant lot that can be used as an urban garden.

Here in Detroit there is a growing movement where people are tearing up the foundations on abandoned properties, and farming on the land. I personally think that's pretty cool. Gets fresh organic food into the poor communities and gets rid of nasty abandoned lots.

monitoring the quality of nearby waterways like streams and rivers, so the taxpayer doesnt have to pay for government services

at least thats what my school did

of course theres the regular boring stuff like
-composting, then selling the compost
-worm farming
-litter collecting/recycling (ugg that is so boring)
-installing rainwater tanks for the school (not sure if its popular in america. here in the very arid land of Aust, we definitely need it)