Wladimir Palant and Mark Finkle have both blogged the great news already: development builds of Adblock Plus are now compatible with Firefox on Maemo (Fennec), thanks to Wladimir and Fabrice Desré. You can get the latest here and start browsing ad-free while mobile!
In case you want to see, I took some screenshots of the interesting bits of installing and setting up Adblock Plus in Firefox on an N900. Here they are (they've all been scaled down by flickr - you can click and get the large size if you want the full resolutions ones):
When you tap on the most recent .xpi file, Firefox confirms that you want to install.
You get a couple of transient alerts over the course of installation, but this is the one the browser shows when it's done. You can tap on this to go immediately to the add-ons manager, or go later, at your convenience.
In the add-ons manager, you tap to restart the browser.
On restart, Adblock Plus is installed, and in your list.
And tapping "Options" lets you do the configuration in place.
New York Times without ads! Very cool.