How do I make my blog iPad / iPhone / Android friendly?

I would also recommend WPTouch which now has great iPad support. There is a basic free version which EAMann mentioned but I would recommend the paid version which is only $39 and has a lot more features. You can then customize the look and feel.

The most iPad-unfriendly thing you can do is try to cater for the device with a dedicated theme, especially if that theme is the OnSwipe one that WordPress favour. Please do not do this unless you actively want your iPad-using readers to hate you.

If your blog is WP-hosted, this will be enabled by default. Please go to your dashboard and turn it off.

You site is probably already iphone/ipad/android friendly.

All those phones use native browsers.

I personally use the WP Touch plugin on my site. It automatically detects if the user is browsing with an iPhone (or iPad) and reformats the site into an iOS-friendly layout with touch-sensitive controls. There's an option at the bottom for visitors to display the normal site if they want.

It's a very well-supported system, and I've used it on 3 of my own sites and 12 client sites so far without any issues whatsoever.

Alex King's WordPress Mobile Edition plugin is my favorite:

http://wordpress.org/extend/plugins/wordpress-mobile-edition/