ZipCar - ZipCar is a free mobile app that connects you with rental vehicles just about anywhere in the world. You can instantly reserve a vehicle, and even unlock it directly from the app.
Uber - Uber is a website and mobile app that allows you to get a ride similar to a taxi service from your phone.
Car2Go - Hourly car rental without designated pickup / drop off
Stretch - Uber for limousines (but it's free)
Getaround - Instantly rent cars near you. Rent nearby cars, trucks, and vans, by the hour or day.
Lyft Line - Shared rides along shared routes, priced for daily use