I'm thinking of ocing the corsair dominator ram (4-4-4-12 @ddr2 800 default) up to ddr2 1066. Is that a safe overclock? Will I likely have to decrease the timings?

more than likely you will have to do a 5-5-5-15 set up, to get to 900, not to mention increase the voltage on the ram is well. And just for notes. OVERCLOCKING IS NEVER SAFE.

when I said safe I meant it as relative to other oc clocks. The dominator ram is covered by a life time warranty, so its as safe as it gets. although, idk if the warranty covers ocing. Probably not.

It probably will cause you intermittent problems with a leap like that. Only way to find out is to try it...
The warranty is usually limited to its stated performance and settings. Read your warranty carefully.