Possible Duplicate:
What are the most important things I need to do to encourage Google Sitelinks?
How do I get Google to display the navigation for my site like it does for others?
For example, take the search results for 'Microsoft':
http://files.quickmediasolutions.com/google_example.png
How do I get my site to display navigation like that? It's already the first entry for certain keywords.
Google seems to use an automated process for determining if such sitelinks are useful for any given site.
We only show sitelinks for results when we think they'll be useful to the user. If the structure of your site doesn't allow our algorithms to find good sitelinks, or we don't think that the sitelinks for your site are relevant for the user's query, we won't show them.
http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=47334
There are several SEO articles about this topic (like this one). Ultimately, it is guessing game as Google does not reveal its algorithms. It seems though to favor 'established' sites with with these sitelinks.
Also of note, Google will almost always only show this for the very first result for your search.
