First off, I'm convinced there are a lot more shields to come. We're already seeing new weapons since the last time we discussed Ulduar gear, I'm sure new shields are coming too. For now, we have three contenders to discuss.
Pulsing Spellshield - Yes, the spellpower is too low. Way, way too low. I've read that on the PTR it has 73 spellpower and not 37, so if it drops, bank it for the future. Although to be honest, even with 73 spell power, it's really not a terribly compelling upgrade over the Voice of Reason from 25 man Naxx. (Then again, the VoR is a Kel'Thuzad drop, he drops iLevel 226 items and this shield is ilevel 219.) Once the stats are corrected, however, this shield will definitely be an upgrade from the Aegis of Damnation, which also drops in a 10 man instance and as such is more comparable. Until they fix that spellpower, however, this isn't worth getting unless you need the stam for a particular fight. This drops from XT - 002 in normal mode.
Ice Layered Barrier - this is one of the nicest shield options for a resto shaman in Ulduar. It compares very favorably to the Voice of Reason, with a slightly different spread of stats favoring mana regen over crit and with a touch more haste. However, while it's a very nice shield with a iLevel of 226, at this point it is probably significantly harder to get than the VoR, since it drops from normal Hodir on hard mode. (Then again, we're already seeing reports of hard mode boss kills, so maybe I'm just being a grouch.)
Wisdom's Hold - And here we have the shield all elemental and restoration shamans are going to want. With a socket for flexibility and comparable to superior stats to VoR (less crit, a LOT more haste, and a whopping 1 SP more) I do think that it could be buffed somewhat for a 25 man hard mode drop. Frankly, the massive stamina over other stats concerns me. Yes, there's a lot of AoE damage in some Ulduar fights, but I still think this would be an excellent shield with 10 or 20 of that stamina converted to spell power or crit. Then again, it's an excellent shield now. I'm still of the opinion it could use a touch more spell power.
Remember my rant about spirit? Several of the rings in Ulduar are just loaded with the icky stuff. Still, there are non-spirit options that I'll discuss in more depth (and then I'll just list the other caster rings). My suggestion is to let the priests, mages, druids and I think warlocks fight over the spirit rings.
However, let's not forget that enhancement shamans exist. Since we just talked caster shields, we'll now switch gears and discuss the ring options for them first.
Band of Draconic Guile - 129 AP on a ring isn't bad at all. The haste scales with Maelstrom Weapon, allowing you more chances for an instant cast LB, so all in all I'd call it a solid choice for enhancement. However, I might still prefer the next ring over it, assuming I couldn't get both. This ring drops from Razorscale in normal mode.
Loop of the Agile - It's a higher iLevel than the Band, which means it's probably a hard mode drop from Iron Council. (iLevel 226) More AP, with crit rating instead of ArP (I know they buffed ArP for shamans but with magic damage coming in from Maelstrom I like a stat that can help with that too) and a gem socket.
Bladebearer's Signet - This zone drop from heroic Ulduar has one reason I'm even mentioning it, since it's a STR ring and thus poorly itemized for an enhancement shaman (we only get one AP from str now, so a str ring usually will have half the AP for a shaman that an agi/AP ring will) - that large amount of expertise. Even with the new Unleashed Rage granting expertise, it's not a very often seen stat on mail gear aside from enhancement tier sets, so if you're low keep this ring in mind. There's also Sif's Promise, but I'm already risking getting you killed by every warrior, DK and paladin in the universe as it is. When looking at expertise rings, please always consider if it's a strength or agi/AP ring, and if it's the former it's probably best to pass to strength loving classes just so you can make the argument that you should get priority on Vulmir.
Godbane's Signet - Now, this ring? This ring is exactly what you're looking for in an expertise ring. You will of course be fighting with rogues over it, not much you can do about that, but at least the strength classes won't try and poison your milkshake over it. This is a Yogg-Saron drop in 25 man.
Cindershard Ring - Heroic Ignis drops this ring, with good agi and AP and hit rating as well as ArP. Even with Maelstrom jacking up our magical damage, we do a lot of bashing and chopping, and armor does tend to hinder our efforts there.
Metallic Loop of the Sufferer - With haste for Maelstrom stacking, crit, Agi and AP this is a solid ring for enhancement. (To a degree, when a ring is really good, there's not much else to say after a while.) This ring drops from General Vezax in 25 man.
What about casters, you say? I say behold the Frozen Loop. Hit, haste and spell power for your demanding elemental shaman. You can loot this from the Cache of Winter after defeating Hodir in 25 man. The only other option for an elemental shaman (who, after all, doesn't want spirit or even MP5 on his or her rings, since mana regen isn't the main concern for them and they have no talents that make any offensive use of spirit) would be the Pyrelight Circle from 25 man Ignis.
If you're doing 10 man content exclusively, elemental shamans, you're probably going to have to eat some spirit (at least until more rings are discovered). If it makes you feel any better, 10 man resto shamans are in the same basic boat for now. The best healing ring for shamans in 10 man Ulduar is the Fire Orchid Signet, which drops from Freya 10 hard mode. With stats befitting an iLevel 226 item and a gem socket, elemental shamans might even want to suck up the MP5 because at least it's not spirit.
In 25 man content, resto shamans will have the Radiant Seal from heroic Iron Council and the Ring of the Faithful Servant from heroic Auriaya. (And if you're okay on MP5 the Pyrelight Circle's not bad at all for resto either.)
Okay, next week we may take a break from Ulduar (we've been discussing the gear here for weeks now and we're not even half done and there's more stuff we don't even know about yet, so it's not like it's going anywhere) and instead we'll shift gears to talk about Flametongue Weapon, Frozen Power, and Enhancement shamans since 3.1 came out. Unless we don't. I like to keep you guessing. There's also this alarming post and blue response to consider.