Are humans evolving?

Yes we are. In general the speed of evolution depends on how well an organism is adapted to its environment. If it is really well adapted then evolution will be slow because there won’t be many beneficial mutations. On the other hand it is not very well adapted – so there’s loads of room for improvement – then evolution will occur quickly (relative to geological time that is!)

The authors of this paper write:

‘The past 10,000 years have seen rapid skeletal and dental evolution in human populations and the appearance of many new genetic responses to diets and disease.’

They go on to find evidence for selection pressures acting on the human genome.

Postscript:
I should say that this only shows that we have been evolving over recent millennia. Now, with the globalisation of the worlds population and healthcare that can actually preserve disadvantageous genes in the pool, things might be very different.