You can't go wrong with
this one , and at that price. This lens has an almost cult following (note the reveiws!). Plus, it's super light and small - so it's a FAB walk-around lens.
You have total control over the aperture, which is so fun. This lens is wonderful for the aperture priority setting

. Also, great for low light settings.
I love
THIS guy's flickr - and this is his set of 50mm Prime (a selection) pics. He may be using the more pricey 1.4 Nikkor Prime lens, but regardless...this is what you could do w/ a prime....
There are other options too, but more expensive...depends on where you're at, but I LOVE the 1.8...love it!