Many MBA schools actually have rolling admissions, usually its the top 20 or so (very school individualized) that does it in rounds.
While some might think "the grass is greener" on the other side by going to business, if you have no business experience you will have a problem getting into an MBA program most likely. Many programs require a few years business experience and some even require certain classes such as accounting/finance/statistics.
With that said you might be able to do a dual degree program if you have interests in both. Its not "too late" for the GMAT's and MBA programs but if you are looking for a competitive program (top 20) your chances aren't as high as the applicant pool is a little larger now than if you would have applied in the Fall/winter.
Let me post here before everyone jumps on the high and mighty MBA.
First read the post above...especially the highlighted section.
1. You need work experience before you can get into business school. Unlike medical school, you can apply from undergraduate only if you go the MD/MBA route because business school will count MD training as work experience.
2. GMAT math test the same math subjects as the SAT but it is by no means comparable. GMAT happens to be a computer adaptive test (CAT) and trust me, you've never seen probability and statistic get so complicated. (CAT adapts to your knowledge(right vs wrong answers) and gives questions based on that.
3. Full time MBA take 2 years, not (1-1.5 years) if done seperately(without MD). It's even longer if it's not done full-time. The only MBA I can think of that awards the degree in less than 2 years is the executive-mba(E-MBA) and you need to be a executive(mid-level manager) to even apply.
4. Unlike medical school, the business school you go to matters. How much job opportunity you recieve will be based on your school reputation (that is, recruiters come to the school) and connections with classmates and alumni.
5. Gunners (not saying you are one) usually are bad fit for b.school because the community relies more on team based projects and the grades reflect that. Anti-social students not welcome.
6. There are probably more, but I'm getting tired. Plus I have to get back to the HIV thread, it's getting interesting there.
P.S.
This message was not addressed to mshheaddoc, I only needed to reference her post.
mdapp06
. if im gonna be out of school for 2 years, i wanna do something useful and challenging, and would definitely love to stay in school. mba programs take 1-1.5yrs, and since i would be retaking my mcat this/next year, completing my amcas for 2009 entry, and hopefully interviewing in september-dec 2008, i would have roughly a sufficient time frame to complete an mba. gmats are administered practically every day at testing sites, which makes it all the more convenient. 
