I've never been a fan of trackpads or the eraser-head pointing sticks on portable computers. I guess I'm a creature of habit, but my productivity takes a nosedive when I have to use a trackpad (or worse - a pointing stick) instead of a mouse. In some cases, especially while travelling, there's no room for a conventional mouse and I've had to use the Powerbook's trackpad. Atek's mini-optical mouse however is so tiny you could even use the Powerbook's surface if need be. It's an optical mouse and therefore usable on most any surface as well as not having a ball to clean. The downside is cost ($49.95 list) and the small size takes a bit of getting used to; although it's head and shoulders more productive for me than a trackpad or pointing stick. The raised plastic ridge helps serve as an index point for your thumb and fingers, something not seen on some other small mice and a plus in my opinion for one this small. Atek's primary appeal is for the traveller that wants the smallest mouse possible, both in carry space and workspace.
The photo below shows the contents of the Atek package which includes a printed manual and a padded travel pouch. There's no software included (or required), althought if you're not running OS X, you need to download their control panel to assign functions to the 2nd button. (Atek notes that their software is not compatible with Power On Software's "Now Up-to Date & Contact". They recommend using USB Overdrive as an alternative.)
The cable is very thin, which is good thing since if it had any mass it would be clumsy with a mouse this small and light.
The next two screenshots show the two tabs of the Atek Control Panel. The two mouse buttons can be assigned various keystrokes/functions. (Of course the left mouse button would normally be left at the default setting.) The screenshot below shows the "Buttons" tab options brought up by clicking on one of the mouse buttons in the panel.
The Pointer tab of their Control Panel has the option to either use the standard system mouse speed settings or overriding them.
To get an idea of just how small the Atek Super Mini Optical Mouse really is, here's a photo of it beside a standard (Logitech) mouse.
I saw a similar sized mouse (just slightly larger) at Radio Shack recently for $19.99, but have not used it so I can't comment on its use or the quality of construction. (It did have a larger left mouse button than right one, which might be a plus for a mouse this small.) The Atek mouse seems well made, although expensive.
For sources of the Atek Super Mini Optical Mouse, see their where to buy page.