Loving central NJ. An hour to NYC or Philly and a TON of stuff here in NJ. There are homeschool groups (religious and secular--although more secular) and a lot of the big things like Franklin Institute and Liberty Science Center (among others) have "Homeschool Days" where admission is either free or greatly reduced.
Add to it that we answer to nobody: no registration, no attendance, no reviews, no testing... nothing.
The best is that an hour in any direction and you have farms (and some awesome 4-H clubs), hills, beaches, city or whatever. Nothing is very far out of reach.
As for plug-ins, there aren't a lot of free stuff (there are a few coops and the Somerset Co. library system has a LOT of free kids programs, but the coops are usually a drive) but there are a TON of enrichment classes everywhere... language, arts, sports (arts and sports might be free through your municipality's recreation dept. depending on where you live).
I'm currently living where Somerset, Union & Middlesex Counties connect and I love that it's central to everything but with the benefit of the Somerset Co. library programs (kids from birth through teen at any county branch). I can get to Princeton in 45 minutes (non-rush hour) where they have a coop and homeschool choir plus a great pick-your-own (just about everything) and I have a ton of enrichment programs in Union Co. I have my choice of 5 YMCA systems in easy distance (read: 15mins or less), and a free kids nature museum on a reservation with great hiking trails and super cheap kids programs within 10 mins. plus horseback riding stables.
I could go on and on, actually. Tell me what you're looking for (a list) and I'll tell you how many I have of them within your acceptable drive time. Seriously. Every time we considered moving out of state, it was HARD to leave NJ for all the homeschooling amenities it offered (among other things). I never thought I'd find it hard to leave NJ! LOL! Now we're being forced to relocate.