No ideas on adventures, but since you're a 1st time DM there is something which cannot be stressed enough....
DETAIL! As in don't let combat become an endless math lesson.
Instead of "Ok, you get a critical on the orc with your longsword, deal it *roll dice* 17 damage, it dies.", say something like "Alright, a crit! You rolled it's exact AC to hit, nice. How much damage? 17 with a longsword. You swing your blade at the orc, who tries to parry with his shield, but your sword crashes through his shield, severing his arm at the elbow and deeply slashing him from shoulder to hip. His guts and organs spilling out as his mangled body hits the ground with a sickening *THUD*, a pool of blood forming on the stone floor." Now THAT will lead to some satisfied players.
When describing surroundings, don't just say "There's some trees and a river to the right of the path.", say something like "As you walk down the well-trodden forest path, you hear the wind rustling through the amber leaves in the tree branches above, the occasion beam of sunlight breaking through the thick canopy to form a myriad of lights bewteen the trees. The sound of rushing water eminates from the wide river to the right of the path, and you see a bear batting salmon out of the water on the far side of the river."
Come to think of it, Blackshirt5 could learn a lesson or two in describing things.
