Kitely is the biggest commercial provider of OpenSim regions, hosting more than 17,000 regions (as of January 2018). Kitely is considered to have the most user-friendly administration tools in the entire OpenSim hosting industry.
Work on Kitely began in 2008, with the vision of enabling people to use virtual worlds as an on-demand utility. It took the company more than two years of intensive development until it was ready to start its public beta in March 2011. Kitely is now the leading provider of affordable high-performance OpenSim hosting solutions.
As of today (July 4th, 2018), Kitely has 103,725 registered users and 17,549 sims or regions, according to the statistics on their login screen. They seem to have a healthy marketplace, with thousands of items for sale. Kitely has their own currency, called Kitely Credits, which you can use to buy things.
The one thing that drives me crazy about Kitely is that many unvisited sims are stored offline, and you quite often get the following message when you try to teleport from one place to another in-world:
Basically, you have to wait until the sim you want to visit is restarted, and then you are teleported to it automatically. The delay is usually less than a minute, though sometimes it takes longer. But I still do find it annoying, especially after years of being able to teleport instantly to other locations on other virtual world platforms like Second Life. The tagline for Kitely is “Virtual Worlds on Demand”. and they aren’t kidding about the “on demand” part!