With the ever growing trend of mobile browsing it makes sense to offer your readers a site that is mobile ready and saves the reader a great deal of time waiting for image heavy pages to load and such.
You can work something up in PHP which will allow the blog to detect when a mobile device accesses it and offer the mobile theme, for example Chris Coyier found a solution a while back (Redirect Mobile Users to a Mobile WordPress Theme)
Something like that requires a fair bit of PHP knowledge and may not be the solution many blog owners crave, this in mind I have listed a number of plugins and mobile themes that will allow you to easily detect mobile devices.
Mobilize by Mippin
The Mobilize by Mippin plugin is a cost free solution which no configuration is required. It directs mobile users to mippen.com where your blogs feed is rendered out in a mobile friendly output.
WordPress Mobile Edition
This plugin shows an interface that is suited to mobile devices, the plugin detects mobile browsers automatically, but can be setup to support more by adding user agents.
Mobilepress is a flexible solution to offering users mobile support, it allows creation of custom mobile themes for various devices. It also has in built support for ad networks and is SEO enabled and can detect search bots.
WordPress Mobile Pack
The WordPress Mobile Pack offers a number of tools that will support mobile browsing, with tools such as a switcher, widgets, themes and a mobile admin panel it is packed with options.
WPtouch transforms your WordPress install into and iPhone app style with has smooth ajaxified loading effects. Most mobile devices are supported. Most of the plugins appearance can be altered and offers a switch to allow users to choose between the mobile and regular theme.
Wapple Architect Mobile Plugin for WordPress
This plugin uses Wapple’s web service tools which allows greater detection of mobile devices, the plugin also allows you to keep the styling of your current theme and doesn’t force you to use a default mobile theme.
WordPress Mobile by Mobify
This detects mobile devices and sends users to the appropriate URL, it requires registration at mobify.me to create and manage your mobile version. It is styled with CSS and allows a good level of customization.
There is a free version as well as a paid version of mobify.me, obviously the paid option offers more freedom.
Again this plugin offers automatic browser detection. It includes a mobile theme and optimizes images for mobile devices as well as supporting ad integration, commenting and search functions.
I hope this article has perhaps given you some inspiration or direction, I can’t tell you which solution would suit you and your blog best, you need to opt for the plugin which compliments your site and its objectives.