Here are some ideas that I have tried recently that have found the hard to find needle in a haystack - trust me they work the miracles when the chips are down and you need to find your rock star diamond hidden in the rough:

Candidate pipelining - build the network and they will come - on LinkedIn join user groups of which you can have 50 - create a compelling blog which lists your latest opportunities and post to the user groups every two weeks.  Soon compelling candidates will find you as you tweet, facebook friend, and Linkedin to incredible candidates - just enough to whet the appetite, if you build the network they will come.

Job Board Sourcing - check weekly and continue to look for new candidates that fit your needs as they upload their resume, and then be the first to call them.  You'll beat the crowd of folks trying to get your number 1 hire.

Look for Professional Associations and send the job description to the board members who oversee the professional association, often these associations will have free job posting not to mention may have access to tons of candidate referrels, whet their appetite and watch the stars come to you.  Here is a comprehensive listing of major professional associations - a wealth of information - thanks Mr. Weddle!  -

http://www.weddles.com/associations/index.cfm

You can always google professional association and your desired job function to find what you are looking for.

Look for little known nuggets of Government funded programs where great candidates affected by the economy have gone to find help: in CA we have CalJobs, which candidates must register on - if you post a job you have access to a free job board and can search profiles.  Ahh, the diamond in the rough found in a little known place.  Volunteer for the community associations that support job seekers and Viola networking yeilds the hard to find candidate in a little known place.

Networking - as powerful as ever, needn't be so hard - join Facebook groups, post jobs to alumni forums on the social media platforms, contact local universities to find out who lurks in thier alumni groups, and find the conference speakers who are industry phenomenons and connect with them.  Recruiting success is harnessed when your networking pipelines are filled to the brim with solutions others just don't try.  As well calling these folks direct will always yield success and a name or two.

And that's my sourcing success tips for today.