There are a few packages around.
Memory Map mentioned above is a very cheap one. It does fine if you only want to fly in the UK, and are happy seeing a UK CAA chart (updated whenever a new CAA chart comes out), and no airspace warnings.
If you need something more advanced, allowing worldwide mapping, pc/mobile device flight planning, airspace warnings, updates every 2 hours, proper declutter routines (which you can't obviously do with anything displaying a paper chart), text the right way around when flying track up etc, then try PocketFMS. There is a 30 day free trial here, so you can see if you like it and if it suits your needs, before spending any money
Home of the PocketFMS Foundation.
For the sake of clarity, I should point out that I am a Beta Tester for PocketFMS, but I have no financial involvement.