I've played with some T8 LED light tubes from china which can plug directly into a normal T8 socket (just remove the ballast).

Cost of those tubes averages around $40-$50SGD (those made by ang mos cost double!) after shipping but the brightness (or coverage) is nowhere near as bright as a PL.
Pro is that it'll only light up whats under it, no wastage and would not make it so bright that it'll be an eyesore (try sleeping or watching TV near a lighted aquarium)
Con is that more tubes are needed to get decent brightness...

If I'm not wrong, the smallest tubes in the market are 2ft lengths...so smaller tanks cannot use

For smaller tank, some super bright LEDs or LED strips can also be bought locally that are rather bright that runs on 12V. Sure beats those "desk lamp" type that have only 6 LEDs on them...makes the tank look like its MAMBO night at Zouk...dim and surreal :P