I use an old white MacBook for most of my work. Because my main development platform is Microsoft SQL Server, I run Windows 7 on it using Oracle’s VirtualBox.

In general I prefer editing and managing my code in the Unix environment. I write stored procedures, migration scripts and database schemas in vi in the terminal, and use sqsh to compile and run them.

For interactive work with the server, I use SQL Server Management Studio and to write C# and Visual Basic code I use Visual Studio.

For version control, I stuck with CVS for years, but have reluctantly moved to Subversion because the tools are now much better (TortoiseSVN on the Windows side and the excellent Versions on the Mac).  I still use the svn client in the terminal for a lot of stuff though.

If I venture into server-side stuff such as Ruby or PostgreSQL I have a few Ubuntu servers on VMWare ESXi that I keep around for this purpose.