You, and all the other people that ask this question, have the wrong approach - most FOSS projects are not looking for volunteers, they are looking for solutions to their problems.
To get involved with a FOSS project:
- identify an area of computing you are really interested in
- download some projects that cover this area and play with them
- choose one project you really like
- for that project, pick an area that could use some work - there will always be many, many such areas
- do some work to improve that area - could be code, could be docs
- submit your improvements to the maintainer - they will probably be be rejected, but don't give up, improve further and submit again
- eventually, the improvements will be accepted
At that point you have "joined" the project. Do it a couple more times and you will probably get commit access to the project RCS and then you can really start doing some damage :-)