Seasonic, Corsair, XFX(Designed and built by Seasonic), and Antec for the best ones, there are exceptional units from other brands as well, and there are some let downs from these brands too, like the older Antec Basiqs, so always check for a review.
Select Corsair.. They have a wide variety of PSU's covering every possible wattage range.. To top it up, none of the units produced by them have ever got any negative feedback, be it from reviewers or users.. Build quality and performance are both top notch.. Availability, warranty and good customer support are liking icing on the already beautiful cake..
If you think you find one you like, look for a review of it. Jonnyguru, Hardocp, Anandtech, and that other one I can't remember but has like 10+ pages are good review sites. Read the review and find out who ACTUALLY made the PSU. Most PSUs sold are made by a few companies. If whoever made it is Seasonic, Enermax, CWT/Channel Well Technologies, or Delta your ok. If it was made by Deer, run for the hills.
While you're there you might as well read the review. (or skip to the end and make sure it gets a passing grade.)