I know it's been a while since the last update but rest assured I have still been leveling.
After finishing off north and south STV I mostly leveled through dungeons until I could start questing in Tanaris. It was a fairly fun zone in live and infinitely more so in Cataclysm. Apparently since the ocean flooded inland towards Gadgetzan some people were stranded because of it, and it up to you to rescue them. One of the first quests, given by a gnome, has you rescuing them by piloting a hot air balloon and tossing rocket packs at them while shooting pirates along the way. As if that weren't awesome enough, once finished you exit the balloon and are shot back to Gadgetzan by jetpack.
Unlike on live, Tanaris is absolutely loaded with quests, all quite fun. I've leveled there longer than any other zone so far and still had plenty of quests available before moving on. I especially liked the new arena quests there, like a level 47 Ring of Blood chain but a bit easier. There are also quite a few unique rewards, like a trinket that summons a goblin nurse to heal you. Tanaris is definitely the way to go for leveling 45-50.
Eventually the point came when I had to move on and Un'goro Crater was the next step. Same as Tanaris, you can notice the changes immediately on entering the zone, though it's mainly improved graphics instead of changed landscapes that stand out here. It seems that those mysterious stone guardians have forced everyone out of Marshal's Refuge and they seem to be split between two new neutral goblin camps. As you would expect by now, far more quests here too. There are fun ones early on such as baiting some basilisks into spike traps but there was one here that stands out and I'd have to say is the most fun quest I've ever done.
Maybe 10 quests in or so you can get some from the southern town for the silithid hive. There's one or two standard kill the bugs and loot them quests, but the main one is a 3 man group quest (can be done solo) for killing the Gorishi Fledgling Colossus. It lives at the bottom of the hive and is scaled so it can be done solo but takes about 2 minutes to kill. What makes this so outstanding is that it's essentially a boss but scaled to be done solo or in a small group. There's a periodic poison nova ability you have to dodge each time by breaking LoS and it goes underground after each one, usually trying to get behind you. Elite quests that can be done solo are nothing new but they are generally very easy, with maybe one ability that doesn't do much. I've been told there's at least one quest like this (in Uldum) and if that's the case I definitely look forward to it.
Currently I'm almost at level 54 and will try to update more often. No new vids yet (will when I hit Outland) but I do have quite a few more screenshots in the Worgen Leveling folder on my site, and added one showing water/weather effects. I do recommend you check them out. The water effects improved again last patch, and there are more fun quests than I could describe without making a wall of text.
All screenshots can be found here or using the link in the box to the right.