The following are some helpful links to tools, resources, and whatever else for 5th edition. I am not responsible for any of these products.
Basically everything needed to play D&D.

Kobold Fight Club
An encounter builder.

donjon 5e Tools
A bunch of generators.

Sage Advice
A reference of all WOTC/5e tweets by the developers. Great source for official rules clarifications.

DMs Guild
WOTC-run third-party publishing store.