If you've ever been a part of any forums online (especially automotive forums) many typically have a Classifieds section. They're actually quite nice. You can get some good deals on stuff specific to your interests from some people you may already know/trust to a degree.
What I strongly dislike about these types of things are the people who feel the need to charge the 3% Paypal fee in addition to the cost of the item.
Unfortunately, Paypal only forbids that for online auctions - not individual transactions. It should be forbidden for both.
If you want to use Paypal for your transactions... and take advantage of its simplicity and/or convenience, the 3% fee if what you pay for that convenience. Let me restate that... the 3% fee is what the SELLER coughs up for that convenience. NOT THE BUYER. The buyer is purchasing the item from you for a set price... they shouldn't have to add another % on because you want to use Paypal.
If a seller is that worried about paying that small of a fee - set the price of the item higher and don't say anything about it.
This much I'll guarantee: I will not purchase anything from someone specifically asking a buyer to add an additional 3% to the price for Paypal fees.
That seller can kiss my ass.