Love the site and depend on it for finding new places around the country - great travel resource for me. I'd hate to see it go.
Asking for donations and selling magnets may bring you some cash, but it's not a long-term solution.
Sell subscriptions already. There's a devoted following who would gladly pay. Your site's greatest value is the postings database. Make the site free for all current postings (< 2 weeks?). Charge something like $25/year or $2.95/month or whatever for access to the database. I'll bet you'll get many many subscribers.
(Btw, F***edcompany uses this model and brings in $80,000+ per month in subscriber revenue. Though the content couldn't be more different, your sites have very similar models -- a niche, devoted audience seeking access to info you can't get anywhere else.)
Forgive me if this issue has been asked and answered. I'm just hoping to be helpful.