NuGet for the Enterprise. NuGet. How to create lightweight reusable source code with NuGet. Sometimes, you just have a reusable helper that you bring in to every project (i.e. an argument validation thingy, or the static reflection stuff, useful extension methods, and so on).
You don’t always need them all, they are generally single-file utilities, and having a Common.dll looks overkill or dumb. Loose source file sharing has always been problematic, though: no packaging and versioning mechanism (unlike an assembly), hard to integrate with source control systems (SVN has external repository mappings, but nothing like that exists in TFS or Mercurial, AFAIK), and so on.
NuGet Gallery. NuGet Must Haves.