I don't think it's melting down so much as EI has been out, the controversy is over, and it's a standard method now. A lot of the fears and criticism that came with it (as with any new method) have been dealt with. Now it's time to settle on new projects.
I'm still going to be very active over on TBR, but the holiday season and the cold weather kills plant shipping as well as my desire to sit around crunching numbers and reading scientific papers. Too busy with other things to do the heavy thinking on aquariums right now.
Besides that, nobody's asking the questions right now; EI is understood, so I don't have to go doing math for people to show them how to fix their dosing. I'm hoping to change that some time before spring by getting into experimenting with other compounds that are less frequently used. Some chatter on urea, phosphoric acid (good 2 in 1 KH drop and fert perhaps, good for apisto spawning, has some other possible uses) and other compounds. It'll go along with some more fert deconstruction/reverse engineering articles.
There's also more serious work that Tom has been doing on making affordable CO2 meters that's hopefuly going to change the hobby in a big way by making them around the same price as PAR meters rather than $5,000 lab equipment. I'd love to see TBR shift its attention to the science of flow dinamics.
I do agree that the better posters deserved a few more stickies; there are articles from VaughnH and supercoley that I wish I could access more easily.
The design overhaul has definitely screwed with posting too; I'm going to give it a couple weeks then maybe toss in some suggestions if nothing changes.
Anyhow, thread jacking aside...
Here's some links that I find myself looking through now and then. Many of them have a focus on the science rather than basic methods:
http://www.esf.edu/efb/schulz/Limnology/Limnology3.html - Some course work and lecture notes related to limnology
http://www.plantphysiol.org/ - one of my favorites
http://www.thekrib.com/Plants/Fertilizer/nutrient-deficiency.html - Good for a quick reference, but doesn't mention CO2
http://www.aquascapingworld.com/magazine/ - Excellent free publication on planted tanks. I've got every issue saved.
http://www.aquajournal.net/ - ADA's journal. I don't trust them to be honest about everything, but I do find ideas worth examining at times. Good inspiration for layout.
http://www.barrreport.com/showthread.php/6243-The-Link-Dump-Thread - My own list of URL's that I update from time to time. Not a serious project, but I'm hoping to grow it into a nice little resource some day.