Same ol' story here, got back into playing with other folks after taking many years off to focus on family. I always played at home during that time and have a small studio in my basement, but I've been doing some casual playing with some guys since late last Summer.
I'm looking to get into more/different musical situations, which led me to look up local jams. Found one, it looked like it'd be fun so I went.
The band hosting it was playing when I got there, they were good accomplished players, I'm glad I didn't look them up online before I went or I would have been even more intimidated than I was

Cool eclectic jazz guys.
When their set was over I asked the guy sitting next to me at the bar how the sign up works since I noticed he knew the band. He tells me, and then I mention I play bass and he says "...no one ever plays bass..."

so I ask if he thinks it would be cool for me to play and he says sure.
So I sign up, the guy in charge tells me "...hmm, we don't usually get bass players..." but all the guys are real nice and there is no attitude and there are all kinds of different players there. I talk to the guitar player in charge and explain that I can't play like their DB player but I can do funk or funky blues (I read they know Meters songs), Levin/Lesh style but I'm not too good at jazz. Cool, no problem.
So I'm the first one up,DB player lets me use his tiny GK amp, which was cool of him, and since we were not really loud it was fine. First song is a fast straight blues. Not my cup of tea, but what the heck.
So I start, and I can't hear myself, and I'm playing HARD to try to hear the notes I'm playing, and now I'm getting nervous because I'm playing "blind" and I start making mistakes...on a I-IV-V blues song

I plod through, we hit the ending and people clap. Semi-fail but not too humiliating.
The next song called was a two chord funky jam and I started playing a line similar to "Constipated Duck" from Jeff Beck's Blow by Blow album. I turned up a little, tweaked the tiny contour knob on the tiny amp and managed to find a setting on my bass that cut through enough to hear myself.
I really wanted to play with the first drummer (turns out to be a familiar guy I used to run into in music stores 20 years ago), but he took a break and another guy came up who was also good. This one went better. I was able to get a groove going, lost my nervousness and got into it, although I would miss the change once in a while because I was getting into the groove and forgot to count measures. Oh well, it's a jam.
In the end, I had a great time, it felt great to play in front of an audience again and I don't feel I embarassed myself too badly to prevent me from showing up at the next one.

I found out the drummer hosts another jam next week, he asked me to try to come down (that was encouraging) and I found a few more in the area so I'll be checking them out.
I also have to give props to the band hosting it - that was the coolest no-attitude jam I've ever attended. I went to a few a long time ago and got sick of the BS, but this was just great and I 'm really looking forward to more.