Here is a great "power toy" for .NET developers, ILMerge.
ILMerge will allow you to combine multiple .NET assemblies into one. This allows lots of different possibilities, the most common of which is if you have a project where some of the code was developed by a VB team and others by a C# team. Using ILMerge you can combine these two assemblies into one to distribute to your customers just like if you had coded them in one solution.
Another possible use, if you have built out your UI in one solution and your business logic in a separate solution you can combine these two assemblies into one. While there are certain values to leaving these as two assemblies in other situations the benefits of a single assembly is more desirable.