Are offers for interns negotiable? I'm sure this varies from company to company, but most startups don't have a formal intern program like much larger companies and probably far fewer applicants and far less recruiting. In general, would it be out of line for an undergraduate to try to get a better offer?
We hire a couple interns a year for web design, development and internet marketing. Interviewing for internships is similar to interviewing for a real job and your starting salary can certainly be negotiated if you feel that it is warranted.
If you are very experienced already and are going to bring a ton of value to the company then they shouldn't pay you the same as an intern that is just starting out. If that's the type of offer they make you then you can certainly negotiate.
For internships you should be more focused on experience then money. The difference in a couple bucks and hour today is not going to be a big difference in the long term.
However, being too greedy and not getting an internship that has the potential to educate you and put you into a position of making much more money later on - could certainly hurt you.
Startups may not have the money - worst that could happen is they say no and you accept the current terms. Well worst they could do is say no and offer the job to someone else, but assuming you are negotiating in person you can try, and if they say no still accept.