Google Custom Search can let your prioritize results

You can use the site: operator to make Google restrict the search results to only websites originating from a specified domain. However, there may be times when you want Google to prioritize results so that those from your favorite websites will automatically appear before results from other sites (which then appear below).

Google's personalized search feature of star-ring results requires manual intervention but Custom Search can automate the process of always moving results from your favorite sites to the top.

Also see:
Google Guide