Your class could start a recycling drive at your school... our school makes money from aluminum cans and capri-sun pouches. They also were able to get money from empty chip bags but I'm not sure how that worked. Might could look into it though.
Another idea is to sell candy-grams for Valentine's Day. Students can pay $1 to send a candy-gram message to another student. Your students could sell the candy grams and help deliver around the school.
Do you teach at elementary or high school level? At my old high school the special needs class ran a coffee shop every morning. In the coffee shop they also sold school spirit merchandise, coffee mugs with their school emblem, t-shirts, etc. It was a HUGE success but alot of planning and work went into it.
Other hit fundraisers at our elementary school include: selling the large stadium pickles at lunch, 1 for $1, set up a school store in the mornings with pencils, etc., $1 hat days, $5 jeans passes for teachers, for our Special Olympics fundraiser one year our prinicpal let me raffle off one paid day off for a teacher. Teachers paid $3 per raffle ticket and the winner got a day off that did not count against their personal/sick leave!! That was a big hit at our school.
If I think of any others I'll let you know.