After Google App. Engine, enters heroku

Heroku debuted a commercial version of their Rails hosting solution recently, after a free beta stage that lasted over a year. They describe their service as "provisionless deployment" because it operates and scales automatically, without any system administration.
It is based on Amazon's EC2 cloud (with its accompanying SLA limitations), but they nevertheless offer solid offering that is worth further examination.

Shared Cluster offer: "Light to medium data needs"

1. Blossom: FREE / 5MB storage / Fits a blog, personal site or small project wiki.
2. Koi: $15 / 50MB storage / Great for a small company intranet or staging server.
3. Crane: $50 / 500MB storage / Perfect for a small biz app, e-commerce site or CMS.

Dedicated: Need muscle? Choose a high-performance / high-capacity database box. Fully managed.

1. Ronin: $200 / 1 compute unit / 500G storage / Guaranteed performance for heavy duty, high-traffic apps.
2. Fugu: $400 / 5 compute units, 1TB storage / Highly concurrent apps with complex transactions.
3. Zilla: $1600 / 20 compute units, 2TB storage / World Domination.

Costs are provided for information, billable per month and subject to change (see web site)