Weirdly, on the iteration of Ubuntu 12.04, someone decided to remove a few settings by default in the system settings menu. The accessibility feature, Mouse Keys, is still present under 'System Settings → Universal Access'. However, without the removed options, it is no longer possible to easily change the acceleration of the mouse. Ironically, this defeats the point of having Mouse Keys as an option at all as the default values make the mouse dreadfully slow, cumbersome, and ultimately quite unusable.
A quick way of fixing this predicament is to install the xkbset package; which allows the configuration of the XKEYBOARD extension. Open up your favourite terminal and type the following to install the xkbset package:
sudo apt-get install xkbset
When the package is installed, a simple one-line command can then be used to configure the acceleration. For example:
xkbset ma [delay] [interval] [time to max] [max speed] [curve]
For those new to command-line interfaces, the brackets need to be replaced by a numerical value – tailored to your own taste of course. I have recently used the following for my configuration; mess with the numbers until it best suits you.
xkbset ma 60 10 10 20 10
Now that you have made mouse keys somewhat usable, other accessibility options can be tweaked using the same package too. For the curious, simply use the following command to discover other helpful tweaks and features: