I don't know much about VisualBasic, and I don't know of an equivalent in the Linux world.
For Pascal, there is the gpc (GNU Pascal Compiler). Haven't used it, but I'm sure it's fairly easy for a Pascal programmer to transition. Similar cases for many other programming languages like C, C++, FORTRAN, etc. Although, I wouldn't suggest any of those to a VisualBasic programmer, there are several options for languages that reside on several platforms. I guess your choice of language may depend a bit on your company policy etc.
Python would be my top recommendation. It's easy to learn, it forces you to write code that is easy to read, and it is multi-platform by default. If you want to deliver closed-source applications you will see that there are a few noticeable differences between platforms. But in general most code that you write will compile on any system. The tricky part is keeping with the folder structure (i.e. C:/Program Files/ vs /usr/share/). But there are os environmental parameters that you can use to avoid hard coding platform specific options. Down side is you have to learn a new language. Up side is you can use the same code in Windows and Linux and MacOSX, etc.
To keep up a GUI for your applications, there are several options in Python. Many Ubuntu developers seem to go for GTK3, which is also available for Windows. Personally, I much prefer Qt4 (you can use Qt4 for C/C++ as well, the Python package is called PyQt4 for the official one and PySide for a community project). You won't have an IDE the same way you do in VisualBasic, but using Qt Designer to create the GUI look makes it easy to then implement it in a code-only IDE (e.g. Wingware IDE, Eclipse, IPython...). So you will have to switch between the GUI-designer app and the coding IDE app. The same is true for GTK3, where you would use Glade to create a GUI.
Python has a default database package implementing SQLite3. That database is rather capable, but there is no GUI to build it as with Access. There are however packages to access most types of databases. Personally, I prefer to stick with PostgreSQL for all my stuff since it is so scalable. PyQT4 has classes for all the major databases in the QtSql module, but there are many other options. You could of course also set up your old Access databases on a Windows machine with ODBC and then you could call them without switching database software.