I carry offline wikivoyage with me on my Android phone. Found it through here, bit outdated though so you might want to build it yourself from the wiki dumps if you're tech savy. I wouldn't use it to find hostels. Got burned twice in Easter Europe because of old hostel information.
I use aard2, which is open source and contains no ads. I have it set to use wiktionary and use it as my default dictionary app. You can set it up to use wikipedia also.
http://aarddict.org/ http://github.com/itkach/slob/wiki/Dictionaries