We looked at Meme Hub earlier in the year on AAWP:
The process is simple, you pick your background picture (the visual root of the meme) and add your own caption (the word branch of the meme). You can then save it into the Meme Hub library on your device, to the Photo+Video gallery of your smartphone, or share it with your friends via Twitter or Facebook.
You can download Meme Hub as a paid-for version to directly support the developer, or an ad-supported version for free, from the AAWP app directory.