I saw this node this morning and I thought right off that find(1) did something like this natively.. it does catch the files last accessed or created within a time frame and execute a command, but I couldn't figure out how to delete everything that was older than the 10 newest. (for the curious it's: find ./ -type f -atime +7 -exec rm {} \;)

but hey, since you can tack commands into find..
find ./ -type d -exec perl -e '$limit="11";$dir="{}";$i=0;@list=`ls -ltF $dir`;print "Directory: $dir\n";foreach(@list) {chomp;$ls="$_";if (($ls=~ m/\//o) ne 1) {if (($i < $limit) && (($ls=~ m/total/o) ne 1) && (($ls=~ m/@/o) ne 1)) {print "keep $ls\n";} elsif ($i > ($limit-1)) {print "rm $ls\n";};} else {$i=($i-1);};$i++;};' {} \;
ooogly, eh? and yeah, it's set up for testing.. no actual rm'ing going on.. but that's easy enough to fix.
this was my fun activity for today.