Deckbuilding Resources

Competitive EDH Subreddit

Subreddit for competitive EDH discussions.

tappedout.net

Site for creating and sharing decklists. Includes tools for counting mana symbols and balancing manabases, as well as hypergeometric distribution stats.

MTGSalvation

Forums are good for discussing card choices. Contains several useful archetype primers.

MTGStocks

Historical TCGPlayer price data. Price charts are watermarked by set release, so this can be used to demonstrate change in demand for cards at a given point in time (eg. before/after rotation, etc)