Finally, don't underestimate end-users willingness to donate. Paypal buttons don't work because everyone assumes everyone else has donated money. We started using "donation trackers" by ChipIn (chipin.com) and they've been quite effective. Make sure you set a "goal" because people love to feel they're helping you work towards a particular amount. (For instance, we always get our most donations at the beginning and end of each month, when people send the donations percentage to 5% and to 100%).
Best money-saving tip: find a webhost to donate a dedicated server; it's the most important way to save money and keep afloat.
