Hello, I'm looking for some advice on how to get established as a programmer, (I am particularly interested in developing interactive, database-driven web sites).

I am a computer-science student who has now taken courses in Java and C. Beyond that, my experience is very limited to just basic HTML and some related concepts like CSS and some basic PHP (which I am starting to getting rusty on as a result of studying hard in school (how ironic)).

I just finished the semester and have a few weeks off. I'm looking forward to learning something new during this time off. What can I do to get myself better established during my time off? I have thought about:
-Certificates (but not sure which ones to go for).
-Getting involved in an open source project. (I'm not sure where/how I can help out with my limited experience).
-Developing some on-line 'widgets' as a portfolio.
-Or ???

Regarding the certificates, I am taking classes next semester on assembly language, 'computer architecture' (whatever that means), machine instruction sets, memory management, , file systems, binary/hexidecimal arithmetic, etc. So, if there is a certificate that I can study for that also preps me for these courses, that could be a good strategy too.

Any suggestion or advice appreciated.

Thanks in advance.