There's a growing number of 'snippets collections' you can download from
this site and elswhere.
These normally come as zipped packages which should be extracted to the
following locations, depending on your operating system.
C:\Documents and Settings\[your windows user name]\Application
Windows Vista or Windows 7:
C:\Users\[your windows username]\AppData\Roaming\Microsoft\Expression\Web
When you've extracted them, make sure they appear correctly in these
locations by viewing them in Windows Explorer or My Computer:
Click to enlarge the image
In this image we can see the HTML5 snippet folder we've extracted into
the mySnippets folder