#3. Blue Cat Series
#2. Kjaerhus Audio Classic Series
#1. Variety Of Sound Suite x10!!
The "BootEQ" and the "Epic-verb" are stellar all by them selves. These are heads and shoulders above the current crop of free vst's that its amazing they are still free. The Epic Verb side by side with the UA/EMT Plate can produce astonishingly similar results considering the price difference.
Its the only free vst that I still use in daily production. The BootEQ is also a unique vintage color that is killer on vocals and a drum buss. All three all a good bit of programing and useful but considering Sonar now has a great set of tools included, you end up using less of them yet the Variety Of Sound stuff is still unique and powerful enough to still be viable alongside Sonar's tool set. The only drawback is they run at 32 bit so they will wrapped. But even under those conditions, they are still a completely useful daily tool.
http://varietyofsound.wordpress.com/vst-effects/