for the original poster, being in zone 7 on the mid Atlantic coast, then this time of year is probably perfectly fine..however if you live further north, there are in fact certain times of year you wouldnt want to introduce new plants to an outdoor bog, if they are meant to stay outdoors all year..August is still probably ok for just about anyone, because there is still enough time for the plant to prepare for dormancy..but you certainty wouldn't want to plant new plants October - March..and I believe no one should order new Sarrs or VFTs in the middle of winter..
Spring is best.
Summer is ok.
Autumn is iffy.
Winter is not very good.
so no, its not really accurate to say "You can plant any time of the year! Any size plants are fine!"
thats simply not true..
it depends how and where the plants were growing before you bought them, and where you live..plants should ideally have as many months as possible to prepare for dormancy..which is why getting new plants in the Spring is best.
My CP page: http://1stclass.mylargescale.com/scottychaos/CP