The following are excerpts from the most excellent Classic Dungeon Designer’s Netbook #4 OLD SCHOOL ENCOUNTERS REFERENCE that I found most usable in my 5E game. While written for 1st Edition, the following files are quite usable in 5E and between The Monster Manual, Volo's Guide, Tome of Beasts by Kobold Press, and Fifth Edition Foes by Necromancer Games, all the monsters listed should be at you fingertips - If you don't have the above mentioned manuals, go get them; you'll thank me later. SERIOUSLY.
DM Adventure Log - B. Scot Hoover (Kellri)
Dungeon Wandering Monsters - B. Scot Hoover (Kellri)
Random Encounters Tables - B. Scot Hoover (Kellri)
For those who want the whole book Classic Dungeon Designer’s Netbook #4 OLD SCHOOL ENCOUNTERS REFERENCE, go here.
Outlaw D&D Character Sheet