Turbos

VS Racing

https://turbo4less.com/

VS Racing is very popular with the turbo LS crowd, in large part to Sloppy Mechanics using this brand of turbos with great success. The prices are great and the customer support from the owner is top notch.

CX Racing

https://www.cxracing.com/

CX Racing is popular for their low buck but well performing turbos and other turbo accessories. Customer support seems to be iffy but quality for the most part seems to fine for the price.

Speed Daddy

http://www.ebaystores.com/Speed-Daddy-Com

Speed Daddy is popular with the Honda crowd for having VERY cheap turbos and turbo kits. Boostedboiz' EK hatch is believed to be using a Speed Daddy GT35 at 600HP for a few years now.

Emusa

(Random sellers on eBay)

Emusa is also a popular choice for Hondas and other four cylinder cars. Not much info on reliability or customer support.

Twisted Motion

https://twistedmotionlv.com/

Twisted Motion provides a large array of budget orientated turbos and turbo related parts. Like VS Racing, they also sell high end, built to spec, turbos.

On3 Performance

https://www.on3performance.com/shop/

On3, like CX Racing and VS Racing, are also popular with the V8 (GM and Ford) crowd.

Rev9

https://rev9power.com/

A popular choice among budget four cylinder builds, from Nissan to Turbo Mopars.