There are so many off shore ones and most offer rebates.
www.betehorse is my favorite as it has a good layout, easy to use, and is starting a section where you can bet against a horse i.e set your own odds and take money against it winning..kinda like being your own bookie which is real interesting when you really hate a favorite and know it's going nowhere.
Having said that, I still use brisnet which is also american tab which is also tsnbet. For one you get all the videos and all the tracks. When you look at the program screen you can click on any horse and watch their last races. So, as you cap and see a comment like "stumbled at start" you can click and see quickly. The other reason I like them is they have racing from England, France, and the rest of the world and you can bet on those.
Since I only use Brisnet forms, you also get a discount on those as well. Finally, it also gives statistical history of your betting. You can look over a year and see how you did in whole, for just certain bets, or certain tracks, etc. It's helped me understand what kind of better I am and where my strengths are. All that is worth the 8% rebate or whatever from the offshores.
Hope that helps...good luck