You’ve probably heard of them already, but in case you haven’t, Thermaltake has a great selection of DIY components for liquid cooling of computers and similar products. They offer both passive and active radiator solutions, plus various ways to cool CPUs, memory, video cards, etc. Pretty extensive. It does seem geared more towards the DIY rather than OEM; if you’re designing such a system for an OEM I recommend you also check out CoolIT; they have some very high quality products and are a good fit for production systems (Thermaltake may be as well, I just haven’t seen their products up close yet).