Is it possible to limit the memory an application is allowed to use?

"I know this isn't a general approach to limiting the amount of RAM available to the applications, but here is a nice guide to limiting the amount of RAM available to firefox.

I'm not sure if there is a general approach to limiting memory usage for single applications (except for maybe java applications)."

"Here's a cure that might be worse than the disease - run the application in a virtual machine. The virtual machine will have a hard limit on the RAM it can utilize.

There's obviously some overhead in creating the virtual machine, but for Firefox you could probably run it in a very small Linux distribution."

"I've discovered Minimem which purports to do what I need.

EDIT: Minimem does reduce an app's RAM footprint every how often you set it (when not in the foreground). However, give the app focus and RAM usage shoots back up unconstrained until the next time. What I'm looking for is something to set a hard limit on app RAM usage rather than trim it every so often."

I know, its not firefox, but k-meleon might be a good fit for the machine -it uses gecko, runs well, and supports some extentions, notably adblock. Not quite firefox, but it works well on nearly identical specs.

The AFOM addon is very effective at reducing memory usage, especially after long sessions. Not quite your full answer, but I hope you find it useful.