any work done on campus is allowed as F1 student, for example most campus has book store maintained by efollet, cafeteria maintained by chartwells...working either on bookstore or cafeteria is on campus even though they are technically not under the management of the campus but rather contracted by the campus/university.
Also if you are volunteering/working for a company that is affiliated to your campus/university, then its considered on campus work and is allowed with F1 status...this applies if you receive your paycheck though that company and not from the human resource department of your campus/university.

In the event that the company that you are working with is not affiliated to your school, and they don't do any work on campus, but the work you are doing is directly related to your field of study, you can apply for CPT (curricular practical training). you can apply for free and processing time is usually 1 day that is also depending upon the working speed of ur DSO. if you are on CPT, ur maximum allowed time is 24 months working part time and 12 months full time. If you cross this limit you loose ur OPT; however your can work for 23 months 6days part time; 11 months 29 days full time as CPT and still be eligible for full OPT.

i know all this because i have taken advantage of all these previledges....

hope that helps...