IBM Mainframes Website
Interesting site from India highlighting mainframe jobs, manuals, references etc.

Mainframe - another community
A collection of opinions from engineers, developers, programmers, users and influencers who share a passion for the past and future of mainframe computing. Lots of useful and fun information here. The History section is great, as it the currency of the information.

Mainframe Executive
Learn what your managers are hearing! Subscribe to Mainframe Executive and see the management issues and directions they are likely to be following in the future.

SHARE
SHARE is THE mainframe community. Two conferences a year and for members, an amazing repository of information.

CMG - Computer Measurement Group
If you do performance or capacity, this site should be bookmarked. For a small fee, you can read the entire archives, BUT anyone can read papers that are from conferences 2 years past. There is a lot of useful content out there.

zJournal
The techies journal, available in the US in hardcopy for free. Anyone can register to read it.

System Z - the modern mainframe
Okay, we admit it...System z can't do everything. Although z's lack of social graces may be endlessly entertaining (see videos below), too much negativity can be damaging to your health. So let's all take a nice deep cleansing breath and think happier thoughts - like what z CAN do. You might be surprised to learn about the unparalleled strength and agility lurking underneath that solid appearance: Cutting-edge technologies; monster utilization; ridiculous virtualization capability; And if not social graces - certainly social responsibility with some serious energy efficiency.

Measure IT
A free online journal offered by CMG highlighting performance and capacity issues, enterprise-wide. Published approximately 10x a year. Also offers retirement and career tips. Extensive archives.

Mainframe Central
Mainframe Central A wealth of information — from inside and outside IBM — about System z computers and z/OS to help speed your success with the IBM mainframe platform

Green Mainframe Blog
IBM's discussion on going green with mainframes

New to System Z - Resource Center
You're hearing about the mainframe everywhere. And now you're thinking the mainframe might be for you. Or someone you work with, maybe even your boss, has told you to go find out about the mainframe. Or you're just curious and want to find out more about this long-lived computing platform that sounds stronger and better than ever. Since you're here, it's also likely you don't know a lot about the mainframe and System z, the IBM mainframe platform. The collection of resources on this page is designed to change that.

CA - On Demand Webcasts
Never get to that webcast you signed up for? All is not lost - look at this archive of recorded webcasts and enjoy at your leisure.

Tech Target - Datacenter
Basic site for all things datacenter, from blogs to articles to tips and events. Start here for loads of good information

Compuware Webcasts on Demand
A variety of recorded webinars on product features and best practices

IBM Hot Topics Newsletters
Learn about key zOS hot topics and features

IBM Message Help
Don't drag out that manual - quickly look at IBM messages and see what they mean - online.

A blog on storage and data management
Monthly archives and blogs in this field. Check out the parody gallery.