Half of the photos on Yahoo's Most Emailed Photos page are girl-girl smoochies. Jezzus Cripes, it's the Fark-ization of West. Civ.
Left radical is 'tree' (木), right is 'dam' (才), acting phonetically to
express 'cut down'. Thus this character means 'felled trees'. Later the meaning
expanded to mean 'resource', and metaphorical meanings of 'resourceful'. Henshall
suggests as a mnemonic: 'Lots of timber in dam of felled trees.'
[note: ZAI is apparently the only on-yomi, both ki and sai are valid nanori.
Taka, though, gives 'SAI' as on-yomi.]