Converting a UTF-8 file to ASCII (best-effort)

I have a file in UTF-8 that contains texts in multiple languages. A lot of it are people's names. I need to convert it to ASCII and I need the result to look as decent as possible. There are many ways how to approach converting from a wider encoding to a narrower one. The simplest transformation would be to replace all non-ASCII characters with some placeholder, like '_'. If I know the language the file is written in, there are additional possibilities, like romanization. What Unix tool or programming language library available on Unix can give me a decent (best-effort) conversion from UTF-8 to ASCII? Most of the text is in European, latin type based languages.