Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Transferslot - Easily buy and sell side-projects
kickSaaS - Cool SaaS (Sofware as a Service) apps, resources, & websites to help you just about with anything.
MicroAcquire - A free & anonymous startup acquisition marketplace
Make - Beautiful and customizable WordPress page builder.
1Kprojects - Neglected side projects for less than $1000.