Gems and Meta Gems

In general, [Bold Living Ruby] should fill every socket unless there is a socket bonus that does not require using a Blue gem color, and where the socket bonus is worth more EP than what the loss of the dps stats on the blue gem would be.

If you are matching gems for socket bonuses, use the following:
Red socket: [Bold Living Ruby].
Yellow socket:[Inscribed Noble Topaz].
Blue socket: [Sovereign Nightseye].

The [Rigid Dawnstone] is always the wrong answer for enhance shaman.
The [Bold Living Ruby] will always be better then [Bright Living Ruby] in a raid environment due to Blessing of Kings.

Naturally the epic BT/Hyjal versions of these gems follow the same logic and you should be able to extrapolate which gems to use.

[Relentless Earthstorm Diamond], Best choice for a meta gem. This gem will scale with your crit rating. The 3% crit damage can be roughly approximated to raise your DPS by 0.03 * Crit Rate. At 30% crit rate this amounts to nearly a 1% gain in damage dealt.

[Thundering Skyfire Diamond] gives 240 haste rating for 6 seconds. This is your second choice for meta gems as it appears to have a 1 minute cooldown. Shaman with lower crit rates (20% or lower, geared in heroic/blue gear, just starting 25mans and KZ) will benefit slightly more from this gem over the RED.

[Swift Skyfire Diamond] will yield a very minor DPS increase - same for [Potent Unstable Diamond]