htop is just htop. It's in the repositories, and can be found on the downloads part of this site.

As for this thread, I tend to have my N900 last one day with a couple of hours of WiFi internet use, around a day and a half with very little use. I use Advanced Interface Switcher instead of WiFi Switcher, but it does the same thing - unloads the wifi driver - when I'm not on wifi, so that helps. I'm on stock battery. Heavy use of constant heavy multitasking/gaming/browsing will eat battery within a few hours. I try not to have too many things eating battery in the background, but *shrug*. I may have some I just don't know about (ones I do know about is SSH server, all the stock stuff, anything Advanced Power and Advanced Interface Switcher uses, shortcutd/proximityd, cl-launcher [I'm not sure how much that does in the background though], and probably a few other things I just don't remember).

This is without the power saving mode for wifi ever set on.