Guerilla Mail is a simple idea with one purpose: to avoid spam. The idea is dead simple: go to the website, it gives you a random e-mail address that's good for one hour, and links to nothing else. Register for sites or whatever with it, and then never worry about it again. Although the web service is convenient, sometimes it's not everything you need. For those cases, one might want to look into using the Guerilla Mail API.
Founded in 2010 and based in White Plains, NY, Ongage has a simple idea for email marketers: we deliver. It uses different ESPs to deliver mail according to which ones are most likely to succeed in reaching a given email address. Ongage calls this concept "micro-deliverability."