These are some of the most important informational resources for a low tech tank:

An experiment on substrates

Crypts and their inflorescence

2Toned's DIY CO2 Sub

Discus Eden's Low light Plant List

Discus Eden's Complete List on Plants and tank Companions

My Summary Of Chemistry

Graeme's sharing of Chuck Gadd's Nutrient Deficiency Symptoms

And for the absolute beginner, who has yet to start their tank, the combined effort of Discus Eden, Bardus71 and mr_c265, which is titled: starting a new tank?