I've worked well with following tech niche:
2. Hotjobs (although not niche, I'd like to list it here.)
And of couse, my site: jobirn.com
What is your best niche in tech? Please list here.
In my mind, best niche should avoiding noise from candidates. They should have a great filter system. Of course, in another aspect, they can reach the max quantity of the niche job seekers (You can check their unique visitor to find how many job seekers visit their website per month on http://quantcast.com