With fo.lk set to become the standard for FS/Wanted items, I have a couple of suggestions, which may have been mentioned before, but bear with me.
Firstly, I think filtering out by categories is an extremely useful tool. So having some sort of tick-box system or something similar would be invaluable, and is illustrated below.
Secondly I think more categories need to be included, such as Mobiles. Not sure what other categories are missing, but Mobiles is an important one to have in my opinion.