You can find things like these online, here's a link for graduate programs (I know you want undergrad, but this is what I have right now):
NRC Rankings in Each of 41 Areas
Like any rank list, don't engrave this in stone and implant it into your brain. Just use it to give you a general idea.
Note that schools generally have "Department of Molecular Biology" as opposed to "Undergraduate Department of ..." and "Graduate Department of..."
In a field like molecular biology, your undergraduate school really won't matter. If you stop at your Bachelor's, you'll wind up being a lab technician and I can guarantee you that your supervisor will care more for things like lab technique, personality, work ethic, etc.
You really need a Ph.D. if you want to advance a career in molecular biology. Even with a master's you will most likely forever be reporting to even the most junior Ph.D. holders (well, maybe not postdocs), who will be the ones more involved in directing the projects while you do more of the down and dirty work.