Only available on DVD, but well-worth watching, would be all the other Attenborough documentaries:
Life of Mammals
Life in the Undergrowth
Life of Plants
I also enjoyed Life of Birds, but the PQ wasn't as good as the other 4 listed above. All of them are amazing programs. BBC has released many of those in gift sets, so you may want to look into picking one of those up to save some money.
I've also enjoyed the "Discovery Atlas" series (DVD/BD), though this is about countries and people, not about wildlife. There was a "complete" set released last year by Image, but these include cut-down episodes for a number of the countries (many were originally 2 hours). The original 4 single-disc releases contain the full episodes.
Gord - TVShowsOnDVD.com