Cloud Providers
DigitalOcean - My favorite cloud provider. Super-fast and easy to setup. Sign up with this link and get a $100 credit for 60 days! Linux-only.
Linode - I haven’t personally used them but I’ve heard great things. Linux-only.
Amazon Lightsail - Offers the cheapest linux VM ($3.5/month, first month free), Windows and Linux.
Atlantic.Net - One year free usage of their G2.1B tier, 50gb additional storage, and snapshots of up to 50gb. Signing up with this link gives you $15 in credit.
Amazon EC2 - Offers 750 hours on a limited selection of machines per month for one year on first sign up. Some services are free forever.
Microsoft Azure - $200 credit and 750 hours per month for B1S VMs for a year (Linux and Windows)
Google Cloud - $300 credit for 90 days and one free F1-micro instance per month (750 hours). Many other free services.