Mathew Manela from the Online Tools Group at Microsoft has written a really cool tool, which adds a feature missing for a long time in Visual Studio: Code Snippet Creation.

The tool, which is available at http://www.codeplex.com/SnippetDesigner allows a bunch of functionality for working with custom snippets.

1. Add a new .SNIPPET file via File-New-File--Code Snippet File
2. Export existing code into a snippet:
   Simply right click on the selected code and press "Export as Snippet".
   
3. Edit snippets (set placeholders, etc..)
   The editor is opened after exporting something.
   Additionally you can later on open .snippet files out of the "Snippet Explorer" (see below).
   
4. The Snippet Explorer
   Go to "View - Other Windows - Snippet Explorer" to search for existing snippets.
   

The snippets you build are stored under the path %USERPROFILE%\Documents\Visual Studio 2008\Code Snippets\Visual C#\My Code Snippets.

You can either insert them via the context menu "Insert Code Snippet"
(Ctrl+K-X) or you can assign a short-phrase (shortcut).

With the shortcut you just need to type e.g. prop<tab><tab> to insert a property code snippet.

You can set the shortcut (and other things as well) in the property window of the snippet editor.