This cleans up address by correcting the case. So many people seem incapable of typing their address correctly (capitalized first letters) that I've had to resort to doing it for them!

It's not perfect and may need a little more refinement but it sorts out most of the problems. I've not fully tested this either but I don't think that you'll have any problems with it. It is weighted to English languages.

For OC 1.5.x and OC 2.x:
This is a vQmod plus one additional file.

For OC3.x use the extension installer.
OC3 version has had an upgrade and now comes with a module to control the settings.

Works for account creation, editing and guest checkout. Can be rolled into affiliate and returns if you wanted to but didn't seem worth worrying about. Will not change existing addresses unless the customer edits it.

It does the following:

Capitalizes First Letters
Capitalizes Hyphen-Names
Decapitalizes short words so you end up with Burton-on-Trent for example.
Decapitalizes certain name words like 'de la' and 'van der'.
Sorts out surname prefixes like MacDonald.
Capitalizes certain address terms like SW, NE and PO.
Has editable exceptions list so you can define more uppercase or lowercase words.