most 50mm f/1.4 or f/1.8 lenses can do the thing easily, do not cost much.. the problem is getting a clear path, and a background which is clean, or at least far away compared to subject to be able to bokeh it into oblivion.
the latter is done a lot here, but i still do not like the fact that it still looks as if it is taken at a mass event.
the framing of the first and last shot posted, with regards to subject, i do like though.