Google's web apps can translate uploaded Microsoft Office documents, but with many caveats involving file sizes and HTML formatting. DocTranslator, a Java-powered web app, runs your Office and text documents through Google Translate and sends them back with the same formatting.
DocTranslator runs entirely in your browser, and uses Java mainly to accept file uploads and send back downloads, so it's not quite as heavy as your cynical experience might indicate. It accepts Microsoft Word, Excel and PowerPoint files in both the standard formats and the 2007 variations (.docx, .xlsx, etc), along with text documents. After picking your file, DocTranslator guesses at the language, then offers more than 50 languages to translate the document to. The languages and services come from Google Translate, so the offerings are likely to grow in the future. That's about all there is to the app — no file size limits, no sign-up or download needed, and it works as well as Google does, which is about the best free option around right now.
If you know of another, better free document translator, though, we're open to suggestions in the comments.