For my iPad, I love citymaps2go...which you can use offline (you only need to connect up when you first arrive in the city, then you can use it offline and it will pinpoint where you are...and I love to pin all the places I want to see in a city before hand and then I can make sure I don't miss something if we are in a certain neighbourhood).
For reading, I love Overdrive...I have my local libraries on there so I can download books for free, and Next Issue where I can read all the magazines I want to kill time on trains and planes. If you get a local pape at home, check and see if they have an online version - great to keep track of what is happening at home.
For before I go away, my packing list is on Packing Pro so I don't forget anything. While I'm on holiday, I have an expense app (it's just called spending on my ipad) so I can keep track of where are money is being spent.
I also love travelpod for keeping a day to day diary that I can share with my friends and family. I've used NoteLedge as sort of a pre-trip scrapbook - whereas before I would have carried a small notebook with things I printed and taped into the book, now I can just put things in my noteledge journal - like, well...notes about what to tentatively do each day, or cut and paste directions/maps from the internet and see them offline.