Hideouts & Hoodlums is a variant of Swords & Wizardry written by Scott Casper of Great Scott! Games. You can purchase the PDFs of the rules, supplements, and newsletter at DriveThruRPG here.
In the introduction to S&W, author Matt Finch states 'Take this framework, and then imagine the hell out of it!', which I think Scott Casper really took to heart when he wrote H&H. In the introduction to H&H Scott describes his love for comic books and 0E D&D as a youth. He had wished there was a way to combine the two passions, and now it seems he created his own solution.
H&H is an old school rules game of Golden Age Superheroes. It features the charm and attitude of those comics while keeping the basic rule structure (or lack thereof) of S&W. Since this game runs off S&W mechanics, Scott makes sure to notate in the text what is directly lifted from the S&W Whitebox rules and it helps show that all in all those 0E rules are very adaptive.
Before the modern age of superhero comics, the stories of the time were a bit more simple and 'pulp-y'. Scott does a good job of infusing that into the game, referencing characters like Doc Savage and Dick Tracy as examples of the main character classes. This time around you have the Fighter, Magic-User, and the Superhero. For the most part the Fighter and Magic-User do not differ from the original game, but the Superhero could be seen as a re-themed Cleric. Instead of turning undead, they 'wreck' things, which is an easy way to represent your superheroes abilities. No trying to figure out if your character's unique powers don't fit the ruleset, the 'wreck' mechanic is all inclusive. Scott also accounts for 'alter-egos' in the form of Superheroes being Fighters when 'out of costume'.
Overall the game is a great twist to the rules you might be used to seeing. Though it's a lot of re-skinned 0E stuff, it just WORKS. Scott also seems to be writing material for the game in much the same way 0E was originally released. In the PDF bundle from DriveThruRPG, you get Book I: Men and Supermen, Book II: Mobsters and Trophies, and Book III: Underworld and Metropolis Adventures. A big nod to the Little Brown Books, the content is relatively easy to digest. Of course, after reading through I was trying to figure out what class Batman would be...
And then I read the supplements! Here again, Scott mirrors 0E, and the first supplement 'Supplement I: National' reads almost just like the original Greyhawk supplement. It adds the 'Mystery Man' class, which functions similar to the Thief but is the 'Bat-Man' or 'the Shadow' archetype. The supplements function the same as the original supplements, adding more things to the existing classes, adding more monsters, treasure, and rule options. Interestingly one includes the infamous body-hit-location rules from Blackmoor.
Scott has also been releasing a newsletter of sorts called The Trophy Case. The PDFs are available at DTRPG but are FREE. They are a nice addition and include a lot of interesting tid-bits like comic history and plot hooks from reality and past comic adventures.
I'd say H&H is a fun variant that is worth looking into. The PDFs are cheap, you can get every bit of material for under $20. A complete game ready for your tabletop. There is one caveat that I should point out. The material is spread out much like the original books. This can make organization a real hassle when you are looking at all the different tables and relevant information.
My recommendation to GreatScott! Games would be to go the way of S&W and compile the books and supplements into one larger PDF/book. The organization of S&W is one of it's high points and H&H could benefit from the same sort of re-work. Further, it'd be neat to see this compiled book placed on lulu.com (or other vendor) for some Print-On-Demand goodness. I'd happily add H&H to my growing OSR bookshelf.
In other words, head over to DriveThruRPG and check it out!