What is the order of acidic strength among phenol, catechol, resorcinol and hydroquinone?
A quick search on says that resorcinol is more acidic that catechol, followed by phenol.

Hydroquinone - strong +M effect and weak -I effect

Phenol - the normal resonance you'd expect in all phenols

Resorcinol - -I effect

Catechol - +M effect, stronger -I effect and hydrogen bonding

Taking these factors into account, it is easy to see why hydroquinone is least acidic. Hydrogen bonding and the vicinity of the $\ce{-OH}$ to the anion (for the stronger -I effect) make cactechol more aciic than the phenol despite its +M contribution. Resorcinol has only -I effect and no counteracting electron-donating effects, which makes it the most acidic.