Since v1.2, WebSphere Portal has had mobile support, including built-in client and markup detection and portlets where you can generate markup for WML, cHTML, HTML, etc. You can scope the markup based on the devices so that the same portlet can generate different markup for different devices.
In addition WebSphere Portal ships sample themes for webkit enabled devices (Android, iPhone/iPads, BlackBerry) that show how to use HTML5 and CSS3 to make native looking experiences in your portal.
The portlet factory tooling has built-in support for generating portlets for devices. Rational Application Developer also has support for an add-on called Mobile portal accelerator, which allows for portlets to be written in XDIME. That allows built-in transcoding to over 8,000 devices and will do image manipulation (e.g. remove images, grayscale them, resize them, etc., ) vary the "richness" of HTML, or even generate VML depending upon the target device characteristics.