I've been more Americana for the last 10yrs but there is a huge crossover with the folk scene. A plugged in bass (usually a Fender type) isn't too frowned on. I actively disliked folk as a kid but I've loved the almost punk rock spirit of the jam nights where someone shouts out "Drunken Sailor in Dm" or "Dirty Old Town G" and away we all go. Great fun. Equally those little uke basses (Kala?) or an acoustic bass guitar is an option too. Although bass has always been my main instrument I've played harmonica, mandolin, banjo, guitar, lap steel, dobro and percussion on the folk scene. All good fun.
Forum wise most of the Musicians Wanted sites have as many folk players as rock players. Americana UK might be worth a go too.