I've take a slightly different direction. Understanding that most of the electronics we use on the road (computer) are either multi-voltage or USB (even my toothbrush charges via USB), what I really need is a short US (for me) power strip that I can plug my stuff into and then a single plug converter for the power strip.
I use a Monster Power Outlets To Go that even has a 110/220 USB port. Into that, I plug:
Anker 40w 5 port USB charger (see post above)
Lenovo Computer charger
I've labeled the power strip as "local voltage only" so I won't accidentally plug a 110 volt appliance into the strip whilst I am in a 220/240 volt country.
That keeps me from carrying around more than one plug converter and all of it (including all the USB cords) neatly fit into my Tom Bihn Snake Charmer.