Want opinions about databases

I have been using Access for 6 years now. I have created a number of small applications that are used by small work groups. I want to get more into the large scale databases that serve web sites or businesses with web front ends. The problem is I do not know where to begin. With Access all was built right in together, usually I will split the database in two (Frontend, backend) but with highend databases there are sooooo many choices. So somebody point me in the right direction. Oh yeah, I have also used Visual Basic 6.0, not that it matters, but just more info.
Thanks,