Is it possible to merge two iTunes Store accounts so we can share apps and other purchases?
Home sharing should allow you to see each other's libraries over your home network, and drag apps from your wife's onto yours and vice versa.  You can definitely do this despite having two accounts - my wife and I have a similar problem.  You may have to enter both passwords from time to time to authorize purchases, though.



I found some help setting this up from "Activating Home Sharing in iTunes".

I believe you can also sort hers by "items I don't have" so you can see what she might have bought of interest to you, although I'm not sure you can automatically sync them.

This SuperUser question seems to suggest that merging two accounts is not an option:
Can I merge 2 iTunes Store accounts?