[circlevvaves]

Maybe not the user experience you're intending, but the The Vaults of Erowid is a decent start.

[redisman]

One of the best and most unique web sites I've ever visited also. It's 90's classic internet but nothing has come along to do things it does better.

[piva00]

One of the most educative ones for drug users as well. Trip reports were always an interesting read, being aware of dosage and effects, reading from others' bad experiences to be avoided.

Erowid is massively educational if you got any interest in psychedelics or mind-altering substances in general.

[maedla]

Reading that as a teenager is what got me interested in psychedelics in the first place. It's great.