I spent the first couple of days with my new 770 installing and uninstalling things to see what's what... until I reached a point where the browser became a bit unstable, and I started seeing out-of-memory messages.

I've trimmed down the list of installed applications, but I still see that even after a restart, the system is using about 53MB, with no apps running.

Is this normal, or is there something left over from my experimentation that's eating RAM? 11MB free doesn't seem like much. Enabling the virtual memory has helped, of course, but I'd still like to know if there's something using excess RAM.

Thanks for any feedback!

There probably is some filesystem cache in the 53MB allocated space.

I got OOM Messages and unstable application behaviour even though swap was only used by a small percentage. I tuned the memory subsystem by increasing /proc/sys/vm/swappiness to the value 10. OOM-killer does not kick in anymore at all - the only caveat is that switching running applications takes longer now.

Installing things shouldn't give you out-of-memory messages. Running several things in parallel might.
As the N800 and 770 use the Unix paradigm free memory is considered wasted memory. Right after first startup you may see a relatively large amount of free memory, but as soon as any application accesses a file the free memory will start to be used as disk (well, flash in this case) cache memory. The next program accessing the same file will then get it much faster because it's already in RAM. This kind of cached memory is only released when an application needs memory for other things. So, for a *nix device that's been running for a while the amount of 'free' memory will tend to be very low. That by itself is not a problem at all.