I recently found this excellent video with Dr Yan of Bang Goes the Theory talking about evolution, using an excellent visual analogy for how random variations lead to diversity. He manages to show the cumulative effects of mutations (his mentor Dawkins will have loved him for that) and manages to slip in ideas about speciation (unsurprisingly allopatric) and even draws a little cladogram. There could have been more Liz Bonnin, but I think that about most programmes.
My only criticism of it is that it does not give the full picture. A lot of laymen mistakenly think that evolution is random and this video does nothing to really dispel that myth. Natural selection filters the random changes and is itself a non-random process. It is natural selection which really makes evolution work, so hopefully they will do a piece on that some time to complement this one. Otherwise, fantastic stuff.