I'm not going to link to the apps below for the obvious reason that I don't want to promote their use (consider this post more of a warning), but if you're using this creep list as a shopping guide, you probably know where to find them.
Girls Around Me
The name of the app says it all. Using info from Foursquare and Facebook check-ins, Girls Around Me plots out all of the nearby ladies on a map for you, complete with their photos and links to any public social profiles. Fortunately, Foursquare cut off the API access to Girls Around me, causing the geo-stalking app to be promptly pulled from the App Store.
On the Rebound & Breakup Notifier
You know that Facebook hottie you've had your eye on? Well she/he is in a relationship. But if you want to be notified the very instant that the once forbidden apple of your eye is available, sign up for relationship status updates from one of these apps (also available as a Facebook app, even creepier!).
Badabing! was designed for one purpose: to hunt for scantily clad photos of people via Facebook. The app goes through your Facebook friends' public photo albums and somehow manages to identify images with pictures of people wearing underpants or a bikini.
No beating around the bush here. Although it's a desktop app and not a mobile app, this one "creeps" onto the list because it knows exactly what it's doing. Creepy tracks social network feeds tagged with location information, then helpfully plots the digital breadcrumbs out onto a map for you to follow.
Facial recognition is a great tool in the hands of professionals. But in the hands of your everyday creep, it's downright dangerous. With Recognizr, you can snap a photo of a stranger from across a room and load it to the app to discover their identity and links to their social profiles. Fortunately, it appears this app never went beyond a beta demo.
Spy Tools and Cheating Spouse Info Kit
This one is more of an instruction guide than a resource. The Spy Tools and Cheating Spouse Info Kit offers users step-by-step directions about how to spy on text messages, email accounts, computers, and cell phone records without getting caught.
Lulu & Playbook
Lulu's been called "Yelp for Boys." Basically, you sign in with your Facebook profile to prove you're a lady, then page through your male Facebook friends, rating them on such important qualities as their looks and spending habits. Lulu's other half, Playbook, turns the tables and lets guys rate girls. Playbook wants to give you a place to "brag to your bros about your hookups." What a winner.