I REALLY want the Premier Equine boots that were posted above, but they're unfortunately out of my budget right now.
I like Woofs for a lower-priced boot. My boy seems to be tough on boots for whatever reason. He's had his black pair for about a year & they've held up decently well, although a velco piece ripped right off of his baby blue pair after a few months. That may have been a fluke, though. The upper-level eventer I worked for for a while took her horse to Rolex in Woof boots.
I really like Nunn Finer American boots, as well. I got mine for half price from tackoftheday, but I've not seen them offered since. Nunn Finer American Style Boot