But, if you want basic nurbs, go for rhino, its easy and you can get some really fantastic results (depending how persistent you are)
Rhino is an excellent full-blown Nurbs based program. With that said, a fairly big learning curve goes along with it.
Recently, a program called MOI (Moment of Inspiration) has been getting a lot of attention. Most people call it a "scaled-down" version of Rhino as it has most of the more common nurb tools needed without the overhead that Rhino carries. It also has far superior Nurb-to-Polygon conversion capabilities so you can export clean to your other 3D-software package. I use it with Lightwave and it gives me the best of both worlds. Best thing is MOI is simple to use and understand and has no where near the learning curve of Rhino. However you still need to have an understanding on how Nurb surfaces work. It is different than poly or sub-d modeling.
MOI sells for $195. A killer price for all it has to offer.
Check it out