BW add-ons, not files
I use two little programs to augment my BW work. I'm not talking about other Bible or database programs, but little things.
1) Dropbox- All of my usernotes, custom versions, etc. go in Dropbox, which backs them up online AND syncs them between my desktop and my laptop. It's still in beta, so whatever you want synced either has to be in the Dropbox folder or else be virtually there via symlinks or whatnot. Eventually, I'll just have it "watch" certain BW folders. I know there are other similar services out there, but Dropbox wins for ease of use, cross-platform interoperability (PC, Mac, AND Linux), and efficiency. 2 Gig accounts free. Watch the demo video here.
2) Autohotkey- This is one of those little services that monitors your typing. When it detects certain keystrokes, it replaces those letters with other text. (It can also launch macros or programs, but I don't use it that way.)
I use this extensively in writing in the notes and editor to expand commonly written phrases, replace common typos (like of/of and the/the) and add the date to every note I write. It's small and easy to use.
What do other people use?