Salesforce Demo Orgs

This contains a list of signup links for demo orgs depending on which cloud you want to learn.
Most of these can be found via Google, but I guess centralizing them here is easier.
 
Basic Developer Org
https://developer.salesforce.com/signup?d=70130000000td6N
Financial Services Cloud
https://developer.salesforce.com/promotions/orgs/fscplayground
CloudCraze / B2C Commerce
https://cloudcraze.atlassian.net/wiki/spaces/CCRZDOCS48/pages/376506347/CloudCraze+4.8+Installation+and+Setup+Salesforce+Classic
This one will require you to butter up your AE to get a test license.
NPSP Trail
https://www.salesforce.org/trial/nonprofit-ee/ 
Retail Cloud
Unobtainable outside of SDO for now.