The Certification Foo node has some interesting opinions in this regard.

My advice would be to find an application you think needs written and write it. :) Share it with people, solicit their opinions, and keep making it better.

If there's an existing project that you're really interested in, then try getting involved with that, too. (The added benefit there is getting experience working with a project team.)

The general idea is to build a body of work that shows what you can do.

- Matt Riffle

Update:

Just for fun, I poked around with Google a bit looking for more opinions on the worthlessness of certifications.

• Larry Wall
• Jon Orwant