Overview
Below is an ongoing list of sites to use for your company or invest into other start-ups. If you are looking to be an investor remember these are not get rich quick schemes and most have minimum investments starting higher than $500.
List
AngelList Venture - https://www.angellist.com/
Indiegogo - https://www.indiegogo.com/
StartEngine - https://www.startengine.com/
Kickstarter - https://www.kickstarter.com/