When working up plots and adventures, you might come across writer's block, a dry spell. Do not panic. It happens to everyone, even me. And when that happens, it never hurts to have a something to fall back on to help you until you come up with something. The internet has numerous resources to fall back on, here are some:
Bob has some original stuff for your super hero game.
83 Free D&D Adventures
Wizards of The Coast has some good links to support their products. The Star Wars Archives has at least one campaign, the Dawn of Defiance. Check out their entire archive, it is worth a look.
This Star Trek site has some links to ready made adventures you may be able to adapt to your campaign.
The internet is not your only resource. Maybe in your filing cabinet in your closet you have plenty of old gaming material from your table top games, just sitting there, waiting to be employed? Old Dungeons & Dragons, Villains & Vigilantes, Champions, Traveler, GURPS material just sitting there, doing nothing.
Now, you might say, "Tom, I am not running a (fill in the blank) game, how can this adventure designed for a (fill in the blank) setting work for me? Well, that can be fun. Throwing the characters into an unusual situation might be an enjoyable experience for you and them both. Running a super heroic or cyber punk game? What if the players wind up in a fantasy setting, clad in different clothes? Is it a virtual reality simulation? Have they switched bodies with counterparts from another dimension? Is a telepath screwing with their heads? Or what if you are playing a fantasy game and the players find themselves on a space station? Half the fun would be them figuring out how their hi-tech gear works. Then the other half is you trying to explain to them why they can't bring it back with them to the magical lands of Ebonwood. Likewise some smart ass wants to take his +5 Saber of Shadows home to Rimworld Station. Trust me, the last thing you want to do is mix genres. That's as crazy as combining peanut butter and chocolate...
You know, that is not a bad idea, provided you realize what you are getting yourself into. A magical boom stick would make for a great source of consternation if the players wind up losing it. They would have to get it back, else some peasant might make himself a king with such an artifact. And scientists would be willing to go to great lengths to capture the artifact that seems to defy quantum science, perhaps even hiring mercenary armies to relieve your players' party of their new toy. Just give it some thought and also have an out; weapons have limited ammunition, batteries go dead. Some magical artifacts are fragile, or magic might fade entirely in a world where the artifact was not crafted.
There is nothing saying you have to use each and every element of these adventures you; could drive yourself and your players crazy doing so. These adventures are to supplement your creative energies, not become a crutch or replacement for it. And pick and choose what feels good to you. Do you not like the map? Ditch it. Hate the NPCs? Lose 'em. Perhaps all you need from the adventure is a kernal of an idea, an ember to spark your imagination again.