This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
It includes various Java hosting companies people have recommended over the years. While the entry level plans often don't include JBoss (or any app server), they all have more full-featured plans that include that.
I personally pay for a virtual host that lets me install and run whatever I want. I just pay for a certain amount of dedicated ram / disk space and I can run my own linux server.
I pay about $25 for an unmanaged 256M RAM / 10GB space / 300GB bandwidth account at vpslink.com. Just remember to run Xen and not OpenVZ if you want to run Java. I run CentOS and use the free HostInABox / LXAdmin control panel for server management, which is not the best, but it gets the job done.