Re: OP and lack of space: yeah, totally spaced the occasional "phantom" sleep image. And it's in my install checklist.
As for using monolingual in addition to some of the manual deletes (like Alexa voice, etc): you can slim stuff down quite well that way. I'm sitting at 5.8GB used (base OS + additional programs + user data). But a couple of caveats.
Seem to recall a thread on the board where you want to be very careful with removing the input methods: that caused some major grief for some people, requiring a complete install.
Same re: binary stripping other architectures: occasionally, you get one that does not behave well when that happens. Seem to recall Office might be one such app.
Another place to save disk space, if you use Safari, is to "disable" the web page image caching that is used by history and top-sites. Those jpegs of each web site you hit eat up space, and could be embarrassing.
1) If Safari up and running: Safari > Empty Cache…, then Quit Safari
2) Bring up terminal
3) cd ~/Library/Caches/com.apple.Safari/Webpage Previews
4) Remove everything in this folder (rm *)
5) cd ..
6) rm Cache.db
7) chmod a-w Webpage* .
(yes, there is a space and a period after Webpage*)
Out of habit, I try to remember to run Safari Empty Cache every now and then to a) try to free up space b) flush any old app related stuff (eg. Java jar or webstart files). Might not be doing much in the disk space realm, probably does more for stability of web-based applications. Overall, doesn't hurt anything.