Good Place to Contact?

I'm interested in offering my services pro bono to some places in order to market a bit more (business REALLY slowed down for me), but I am not sure what places to contact or what to say. Any help would be appreciated.. thanks!

First decide WHO you want for clients, then figure out where they go/hang out - that would be where you would attract their attention.

It's a bit different over here - I mean you guys have a lot of family resturants and things we don't have here.....
What sort of work do you want? Birthday parties - corporate events - nightclubs- kids clubs - festival/markets?

If you are looking for birthday parties you could look for a mothers group and head to the park to meet them and paint all their kids ( keep in mind these kids are usually VERY young... but no advertising works like word of mouth.
This would also work for daycare's as you have access to soooo many kids and their families.

When I was starting out I made signs and lamenated them and put the up in the local parks - I got about 5 jobs from doing this.... I also letterbox dropped my local area.
I put on the sign at the bottom to support local business because people seem to like to hire someone from their area... makes them feel more comfortable.
Put signs up in the local shop windows. Head into the local kids clothing store and ask if they would like you to come up and do some work next time they are having a sale.
Call your favorite charity and ask to be part of their next event.
Contact sports clubs, scout groups, schools, and your local council's event managers.
Look through all your local papers for hotels and pubs/bars having family days and contact them to see if they have childrens entertainment.
Paint your face everyday and wear it to the shopping mall, gas station - whatever.... make sure you have plenty of cards on you.

I don't know if you have kids but for the first 3 months before I started charging I offered to paint at all the parties my kid was invited to.
Alternatively you could look for an agency to do some work for while you are not busy.