Lots of different silicones, hit up your local yellow pages for a resin supplier or Google a local one...
Smooth On offers some great stuff, but you pay for the name... You can get comparialbe resins and rubbers for cheaper if you shop around... BTW the OOMOO is nice in that it's a 1:1 mix, but it's far inferior rubber compared to even cheap 10:1 mixes...
Alumilite offers decent stuff, I'm not a huge fan of their 4 hour cure silicone as it becomes brittle after a few castings... I have used it quite a bit over the years but only for short run stuff... They also offer other silicones that are much better...
Silicones Inc offers decent silicones, a lot of times this will be rebranded by your local distributor as a house brand...
There are also several others out there... But the reason I mentioned the above is that they all offer decent customer support, you won't always get that with the more 'generic' companies... Smooth On probably being the most customer friendly...
My primary go to silicone is the stuff offered by AeroMarine, very decent rubber for the cost, my only complaint is that it has a STRONG sweet smell that lingers for quite some time, some people like that smell... I don't mind it in limited exposure like small molds, but if I'm working all day with it the smell can get annoying... My girlfriend flat out hates the smell of it and I hear about it every time I use it :darnkids
