Well there are many brands and I don't have one yet. But I'm leaning toward this kit, Oil Charge Systems - BUY PRODUCT PAGE / All KITS free usps shipping. in u.s.a.
And basically they take a small amount (compared to the factory oil filter) of your oil and filter it extremely well, usually down to about 1 micron. They usually filter all the oil in the engine several time an hour, which helps keep the oil clean and therefor helps reduce wear. Systems that use the Amsoil filters seem to get great reviews, as far as I can tell the Amsoil filters are very well engineered.
Here is Amsoil's site, AMSOIL - By-pass Oil Filter Mounting Kits
they also offer kits and they get good reviews. Just make sure if the oil return is in the oil filter cap, that it has a tube on so the clean oil isn't sucked into your intake.