Hi there Frank - I'm no expert at performing in public even though I've been doing it for 6 + years, but . . .
Check out open-mike nights if you haven't already and get to know the performers and the person in charge of the night - they usually encourage people.
Check out jams as well - get togethers of musicians who (at least around here) sit in a big circle and take turns doing a song - either we everyone joining it or not - depends on the wishes of the performer.
those both worked for me - also, I keep in mind that I am more critical about my performance that are most if not all of the audience - so i don't worry and just let it happen. (3 pints of the "Black Liquidation" has also helped.)
break a leg!