I've just purchased the Canon EF 50mm f/1.8 II myself.
I believe it's the cheapest lens Canon make, but don't let that put you off - certainly the build quality is 'plasticy', but for the price you can't expect too much!
I haven't had a chance to use it much yet, but I have taken some shots indoors, and I have to say I'm impressed.
The main (arguably only) reason for buying this lens is it's large f/1.8 aperture which allows you to take pictures with an extremely shallow depth of field enabling some beautiful portraits with very soft out of focus foreground/background areas (bokeh).
The large aperture also means that this lens is, as you say, good in low light conditions.
Check out this pic
or this one
to see what I mean (please bear in mind that I'm no pro!)