This will keep you at the front of the interviewers
mind and help them remember you when deciding who to call back
for a second round interview.
Also feel
free to use this opportunity to follow up on the anything that
was raised at the interview. If the interviewer had been interested
in something you had worked on previously, or something you
had written whilst studying then it could be a good idea to
send them a copy of what you have written. This will again show
a willingness to go one step further than your competition and
will provide the interviewer with hard evidence of your capabilities.
One thing
to avoid is following up more than once or twice. Do not pester
the interviewer for a response. Obviously if you haven't heard
anything from them after a few weeks then it may be worth a
quick call but don't call every day for an answer. You'll only
annoy them and make them want to say no.