I have worked on large scale projects using Oracle, medium sized projects using MySQL, and some small projects using Access. All have worked great for the most part. However, I have seen problems with Access and I am not impressed overall. I'm sure Access is great for small single user environments, but I wouldn't trust it with the amount of data our DBA's and Admin's handle.

Of course, we use Oracle for our largest projects. Don't get me wrong, it's great that MySQL has transaction support (finally) and should have trigger support (probably in 5.1), but for large projects I am not convinced MySQL has the scalability yet.

For desktop or a small-medium server? MySQL or PostgreSQL all the way. MySQL has come along way since previous 3.x.x. Unless you can afford a high end scalable database program, or unless you need it, I would suggest going with MySQL and NOT Access.