What is everyone using these days? (Of particular interest to me would be hosting with free usage tiers)
I use it for my rails based startup padseeker.com. It makes pushing code via git as easy as it is for heroku, but it is more flexible, i.e. allows file uploads w/o using s3, you can use mysql or postgres (heroku only allows postgres without another service). It's been overall a good experience, very little down time. Heroku might be better for certain things, but webbynode has been perfect for my needs.
It's not free though - lowest plan is $15 per month. I know digital ocean starts as low as $5 per month. Dotcloud and Appfog are either free or cheap and seem comparable.
I use linode for my VPS. slicehost is similar. They both offer decent publicly available documentation/tutorials, so if you can't find an answer or path in "your" providers docs, you can hop over to the other guy's.
With shared hosting you're a user on their (possibly virtual) server, with permission to do things. You're not root.
pair.com offers shared hosting, I used to use them, very stable and sober company.
http://www.lowendbox.com/ might lead you to a low cost provider, I haven't looked down that path.
I know a lot of people use http://www.bluehost.com/. I don't know if they're more VPS or more shared host. I know a lot of people use it to host actual businesses; a lot of those sites use Wordpress and various shopping cart and payment solutions.
http://www.webfaction.com/services/hosting
Personally I bundle this with Cloudflare and it's been flawless!
Caveat: No CPanel! I find their control panel very intuitive to handle and uncluttered but if CPanel is what you're looking for then you're better off elsewhere
VPS Hosting - Linode(http://www.linode.com/)
Shared Hosting - WebFaction(http://www.webfaction.com/)
I strongly believe in this kind of service - old school hosting is dead meat in my eyes. Shameless Pug: We recently launched our own PHP PaaS
I am personally on liquidweb and aws. free tier on aws is great for testing stuff not on my local machines.
Anyone want to explain why iamgopal's post got marked as link - dead?
VPS: Linode
Other: AWS