By default, Visual Studio 2008 puts the Unicode byte-order mark in front of any file you save. You can override this on a per-file basis by going to File > Advanced Save Options and picking a different encoding.
How do I tell VS to use a default encoding for all files in a particular project or solution? This is drastically screwing up source control, because we have some users who commit files with VS and others who don't, creating "illusory" commits.