In contrast to commercial agencies for arranging lifts you will find lift-offered and lifts-wanted notices where no fee is charged on the blackboards of the student unions, the faculties and the refectories. Freebie online-agencies for arranging lifts are e.g. Mitfahrzentrale.de or mitfahrgelegenheit.de. Commercial agencies, which charge a commission, can be found in the telephone book.

By the way: why not going beyond the arranged lift via car? Some online-agencies also offer train lifts. You can save a lot of money on trains by group-travelling – even if your group should consist of no more than two people.