For a dual-wielding shaman in a raid, you want 17% from Hit Rating. You can reduce this further if you always run with a shadow priest or a boomkin, as they both bring 3% hit, reducing what you need to 14%. If you are an alliance shaman, before cataclysm is released, you are a draenai and thus get a extra 1% hit from passive racial traits. Based on the discussion above, you will need one of the following:

17% = 445 Hit Rating (horde, no boomkin or spriest)
16% = 419 Hit Rating (alliance, no boomkin or spriest)
14% = 367 Hit Rating (horde, with boomkin or spriest)
13% = 341 Hit Rating (alliance, with boomkin or spriest)

Good luck!

Assuming you want to never miss raid targets with either weapon, hit value according to WoWWiki is as follows - direct cut/paste quote from them.

All Level 80 Physical DPS

Dual-wield auto-attack: 886 hit rating

Special DW attack or any type of Single-wield attack (auto/special) or any type of ranged physical attack (auto/special): 263 hit rating

Keep in mind any talent, raid or race bonuses may impact the value you actually need from gear.

The reason they look lime spell hit numbers is because very simply they ARE spell hit numbers. An enhancement shaman, who assuming you want to competatively dps better be dual wielding, deals at a very very simplified ratio around 48% physical damage to 52% spell damage. Your specials are all capped at 66 hit rating with 3/3 DW specialization.

Because the DW white damage hot cap is so prohibitively high, and the fact that of your damage white damage is such a low percentage of your overall damage it is stupid to shoot for that cap at the expense of all other stats.

Since spell damage accounts for more than half of your damage it is imperative to cap this damage. Assuming you have a boomkin/spriest in raid you need to hit soft cap 342 for alliance and 368 for horde.

See also:

http://elitistjerks.com/f47/t20765-shaman_enhancement/#Hit_Rating