Though people have been asking for it for years, developers still need write recursive directory copying routines themselves, and every one is nearly identical. So why doesn't this simple and useful function exist in the .NET framework? Actually it does, if you reference the Microsoft.VisualBasic assembly.
Reading and writing to ZIP files is another common task for programmers. A bit more complex than copying directories, developers often turn to third-party libraries or command line tools. Needlessly in fact because ZIP libraries have been in the .NET Framework since the beginning. You just have to dig them out of the J# runtime (and hope the libraries are not decommissioned).
Moving on to our third example, developers often have to read flat files in comma-separated (CSV) and fixed-width formats. While seemingly straightforward, minor points like escaping quoted strings are easily overlooked. Slipped into .NET 2.0 is VB's TextFieldParser, a general-purpose flat file parser suitable these and other similar file types.
So should these little gems remain "language specific", or should they be migrated to the core namespaces of the .NET Framework? A minor question now, but one that is sure to become more pressing as the new languages F#, IronRuby, and IronPython come online.