What does it look like?

I'll start by listing the different sites where a panorama can be published and embed a panorama from each site. Each sample panorama is embedded using the code provided on the services site and only the width and height modified to fit this page.

Service: Round.Me - Free & Pro Versions
Features: Mobile Friendly - VR enabled - Single Panoramas & Tours

Published using the pro account.

Service: WalkInto - Free & Paid
Features: [free publishing has ads] - Mobile Friendly - Single Panorama & Tours - Hosting Options available

Service: 360Cities - Free & Paid -
Features: Mobile Friendly - Single Panorama 

Published using the free account

Service: Spinattic - Free & Paid
Features: Free - Unlimited Panoramas, Unlimited Tours, Geolocation, Privacy Settings, Friendly URL, Free Plugin Pack, WebVR. Paid - All of the free features plus Additional formats, Larger file size, Custom Signature, Mouse Control Settings, Autorotation Settings, Advanced Plugin Pack, Advanced Layouts Pack

Published using the free account

Service: Google Map Street View - Free
Features: Somewhat Mobile Friendly, Single Panoramas & Tours

Service: YouVisit - Free - Mobile Friendly - Single & Tours

Service: Holobuilder - Free & Paid - Mobile Friendly

Service: Flickr - Free & Paid
Features: Mobile Friendly. Unfortunately the player pinches the Zenith and Nadir.

Yellow Submarine Pig

Service: Kuula - Free & Paid
Features: Mobile Friendly, WebVr Support, Embed Editor. With Pro version you can have unlimited tours, add labels, custom hotspots, nadir and zenith patches, background audio, interactive cards and floor plans

Service: SeekBeak - Free & Paid
Features:

Free Version:

3 Snaps (Panoramas) 1 Team, Shareable URL for each Snap, SBS VR & WebVR viewers, Embed code, Custom Hotspot Icons, Colours & Animation, SeekBeak branding, Standard Hotspot Types, Analytics, No expiry time.

Paid Versions: Pro/Business/Enterprise-Reseller

All the above plus Unlimited Snaps (Panoramas), Custom Branding, Logos, 2D Navigational Maps and many more features that you can view on their Pricing & Add-Ons page.

Note: All paid accounts have a 14 day free trial period. (no credit card needed)