I'm going to assume that if you're still reading this past the title, you're interested in talking about tank gearing for your level 80 and that you've presumably used the Dungeon Finder to level him or her as a tank, but you're certainly not rocking full T9 yet. It's generally accepted that you'll be saving up emblems for that, and of course filling the gaps for rings and trinkets and such as you can. You also may be a DPS player who wants to switch over to tanking but don't have the gear yet.
First off, please, don't pass on tanking gear just because it's blue or dropped in a normal or heroic. Just because it's not iLevel 232+ doesn't mean it's not good. You should be collecting and using upgrades as they drop, even if they won't immediately put you at 35K health. Please remember also that a lot of people ran these instances and heroics back when Wrath first released with 22k or so health: despite what speed obsessed or hyper geared players will tell you, it is indeed possible to tank all the original Wrath heroics in blues.
Take the Nerubian Shield Ring, for example. If this drops and you don't have better, roll need on it. Don't worry that people will lose their shard, don't let people give you grief on gear not being up to some ridiculous standard, just take the ring. It has armor, defense and stamina. If you're there as DPS but you want to build a tank set? Roll need if you don't have better. Just ignore people who give you grief over it, clearly they don't understand how important every possible upgrade is while building a tanking set.
Frankly, a lot of the blue drops that people autoshard now were once required and are still pretty solid for tanking higher level content. I tanked with the Essence of Gossamer for a very long time because it was a 111 stamina in a trinket slot at a time where there were no Brewfest Trinkets, no Black Heart, no Ulduar 10 or 25 and no TotC/GC. If you are an up and coming tank or a DPS who wants to build a tank set and you don't have two stamina trinkets that are better, then why are you just letting folks turn the Essence into a shard? Shards are cheap now. 111 stamina for your tanking set is not cheap.
While we're on the subject, please don't be afraid to run specific normal instances before their heroic versions. Specifically Trial of the Champion, Forge of Souls, Pit of Saron and Halls of Reflection. Not only is the gear available from these instances of equal or higher iLevel to your standard heroic (TotC has iLevel 200 epic drops on the same level as Naxx 10, while the three normal ICC 5's drop iLevel 219 epics and some of those epics are very good indeed) - especially keep in mind that weapons and shields are under-represented on any emblem vendor (in order to get a shield for tanking from emblems, you will basically have to trade down from Triumphs all the way to Heroism) - the normal mode Halls of Reflection shield certainly better than the crafted gear you could obtain that's comparable. Likewise, for a druid tank, there's certainly gear in here you'd be interested in.
Also, don't forget the various lower tiers of emblem gear. While it hurts to step down your Triumphs to Conquest or even Valor (much less Heroism) if you simply can't get an upgrade for a slot anymore and you're swimming in emblems this is an option available to you. It's not always ideal and certainly you would prefer triumph gear. But that's not always going to be possible (there is no belt and only one ring available for Emblems of Triumph). Also, if you're purely running heroics, consider skipping at least one piece of your Tier 9 232 gear for the iLevel 245 helmet or shoulders. I can't speak to the druid options, but for most plate tanks the 245 hat and/or shoulders are worth it.
So in general, if you want to gear up to tank (especially if you're looking to move into the harder ICC heroics or even 10/25 man raiding) you need to be ruthlessly rolling need on any possible tanking upgrade (especially if you actually are the tank on a run: you do not owe people a shard if you can use that gear), running instances where upgrades drop even if they're not heroics, and scrutinizing the emblem gear very carefully to get maximum use of your emblems. If you're managing to collect frosts, in most cases the T10 tanking set bonuses (especially the 4 piece) make getting 4 pieces of T10 more valuable to you than picking up capes and trinkets, but that's a judgment call that's beyond the scope of this post. The only reason to pass on gear that is an upgrade to what you currently have is if you are DPS and there's a tank in the run who it is also an upgrade for: a simple "Do you need that?" can help you figure out what to do there.