I'll second the notion on Tax Preparer.
I worked seasonally (mid-Jan to Apr. 15) for H&R Block for 6 years, moonlighting while I was finishing up my career at Mega-Corp. You can work 20-40+ hours/week depending on your availability. And talk about portability...every little ho-dink town in the US and Canada has an H&R Block office, right? After I moved to Canada last year, I took the basic Canadian tax class and worked for an H&R Block office here in BC.
Don't expect to get rich...in the US I made about $15/hour once I got fast (earnings are commission-based). In Canada it's more like $10-12/hour. But it's fairly challenging work, you get to meet all sorts of people, and on a good day you can help someone--either by figuring out a weird tax situation for them or coming up with a refund that they really need.
I'd also suggest checking out
Workamper News, although I have no personal experience with their services.
They have information about campground jobs, jobs at state parks, national parks, marinas, theme parks, NASCAR, lodges, rv parks, and resorts. This is the "campground host" gig that a lot of retirees do. I got a sample issue of their magazine a few years ago... it also had postings for jobs like picking apples in Eastern WA and the Canadian Okanagan, etc. I like any kind of "seasonal" work, since if it turns out to be a bummer for some reason, the end is always in sight!