Google's currently generation of Chromebooks are getting good reviews and appear to be quite viable as second computers.
I know that everything my wife does on her current laptop (running Ubuntu) she could do just as well on a Chromebook, so when her current laptop kicks the bucket, my first choice for a replacement would be a Chromebook, in which case it would be first laptop I've bought that does not have Windows pre-installed.
I just got one for just that purpose and I can vouch for its suitability. I actually prefer the Chromebook to the $1700 Windows laptop most of the time because it doesn't take so goddamned long to start up when you open it.
I know that everything my wife does on her current laptop (running Ubuntu) she could do just as well on a Chromebook, so when her current laptop kicks the bucket, my first choice for a replacement would be a Chromebook, in which case it would be first laptop I've bought that does not have Windows pre-installed.