need some advice on directions... (a lost soul)

[degeneral]

I just left my lab where I did my PhD for years -and standing here with an Master's in MolBio, and Immunology (back to square one: I started the PhD program with it).
Anyway, I'm stuck with an F-1 visa that expires as I finish school with another Ms degree in August, and I'll have a year of OPT (optional practical training), that I can at least use to get... what? Some training in real life labs? Some inspiration?
Anyway, it's a time to change the course. What kind of jobs can someone holding a Master's in Molecular Biology should look for? How could I explain the fact that I quit after 4 years? Do my years in lab count as experience? Do you think I could switch to other major -like Marine Biology, or Paleobiology? How should I start that? Most PhD programs require courses in their respective majors. I'm kind of lost now, and since I invested so much time, and money (the latter not necessarily mine), I can't just go home with my tail between my legs just yet.
Thanks. I hope this post wasn't off-topic.