Many sites offer to let you post your resume online for free. While posting your resume is possible, consider the drawbacks.

It may not be the most fruitful method of reaching employers. Remember, employers begin with people they know.
It is limited to the ASCII format which is not very attractive.
You lose confidentially with your name, address and phone number available to anyone on the Internet. Your current employer may find out you are job hunting.
Read the documentation carefully and check for costs before posting.

For more on electronic resumes see:

Riley Guide to Preparing Your Resume for the Internet and Posting it Online
http://www.rileyguide.com/eresume.html

Some sites to post your resume at include:

WNYJobs.com http://www.wnyjobs.com
Monster.com http://www.monster.com
Hot Jobs http://www.hotjobs.com