What Jobs Should I Keep on My Resume?

Dear Experts, I'm your basic 'job-jumper' since graduating from college 6 years ago. I've changed jobs 5 times and none of them were in a field I was interested in. But now, I'm really sure I want to get into Marketing. I recently took a night course in it and my current job as an administrative assistant is for the Marketing Department of my company where I've learned a lot about the the field. I've been told by my employer that there are no openings right now, so I want to start looking for a marketing job someplace else. My question is, should I leave off all the jobs I had before this one since they don't really apply (i.e. cocktail waitress, nanny, teacher's aid, jewelery sales person)? I'm afraid they aren't going to take my application seriously when they see all the other jobs I've had. Wouldn't it be better to just list my current job? What do you think? Our Twitter Advice Project (T.A.P.) is no longer an active campaign. To find an answer to the above question, please use the "Search" box in the right-hand column of this website.