Try Gumtree too. Their 'music' sections are full of "bands looking for players", or "players looking for others". Post something there.
But I know it is difficult because we always assume everyone else is better than us! THat's not always the case - they usually have more confidence, but they're not always any better. You just have to break that confidence barrier by getting out and giving it a go.
Of course you help yourself by pitching it at something manageable but there are plenty of good suggestions here.
My experiences...
Concert/Big bands - first one I played in was, with hindsight, too good for me. The conductor was ex-military and retained the standards he'd lived with for many years, which meant cowering behind the music stands some evenings as the baton would fly across the practice room. Put me off for a long time, actually, so don't go there! I've played in others since that weren't anything like as pressurised and it's great fun.
Residential - great idea, you know they're all there because they want to learn and share. Tutors are generally excellent, will push you enough to bring you out, but won't embarrass anyone.
Workshops - I did these for a few months BEFORE I did a residential course. Great experience if you find a good group who are willing to let you have a go, help out, and just let you find your way. If you just bung in a few bars using a blues scale then stop and leave it at that you're on your way. You'll be itching to get back next week once you've broken the ice. The majority of these are mixed ability, people who love the music and want to play. Generally, they all started out like you and are happy to help newcomers. If they are prima donnas who can't abide someone playing a bum note or missing their cue they'll be in a decent band with their mates, not at the workshop. No, the ones who go along to workshops are the sort who are happy to play with anyone just for the fun.
Adult Ed - I've done an evening class workshop (travelled 50 miles each way - that's how keen I was) for a couple of terms, and am currently doing a Saturday workshop at Sussex Uni. These are good, some have more tutoring, or structure, than others but again they have players in the same boat as you. Some are further advanced, some aren't, but they are all there for the same reason.
Small groups - one of the best things that came out of the resdiential course was meeting a few other players who lived near to me. From that we still meet regularly (piano, bass, guitar, alto, tenor, drummer) - this was a really good start as we all knew roughly where we we coming from at the outset so there was no worry about "will I fit?"
Open mic - done a couple, didn't really enjoy them particularly, but that's me. They work really well for others.
Other students - my old teacher put together a sax quartet for his pupils. This was excellent. He selected students who were about the same standard so we knew we were'nt going to look silly, we all knew the teacher so were confident he was going to give us stuff we could do, and it made for a very relaxed intro to playing with others. Do you have a teacher? If so ask if he could get you together one evening.
One thing to bear in mind - you do need some experienced players to drive it forward. If you get together with a complete bunch of newbie's you'll get nowhere as everyone will be looking for someone else to take the lead. Someone has to have the ears and experience to drive it forward.
I repeat, the good, experienced, players who do any of these things are in it for the fun and to share their knowledge. Their serious stuff is probably done in other bands, for them this is a fun way to share their experience so go with it and grab a share of it.