This article explains about creating a "bench" of top talent.

One of our customers wrote a blog to get salespeople and they got 40 people applying.  This enabled them to get have a bunch of people for the current roles and also a block of people for the future recruitment.  In other words a bench of people.  This customers tells us they have saved over £125,000 ($162,000) in recruitment fees.

Of course this gives a one of hit of recruitment, you could get other senior managers doing this or you could create a culture that your company is great and employees great people, through the power of social media.  If you can save £125,000 in sales in recruitment fees, what else could you save if you empowered all employees to talk about how great the company is?