How to backup your account or campaigns or ad groups:
Open/Download your account into AdWords Editor, then click File -> Export backup (AEA) -> choose what you want to export -> Find a safe place to save that archive on your computer
How to restore anything you backed up:
Click on "get recent changes" so you have a fresh view of your account in AdWords Editor.
Click File -> Import account snapshot -> navigate to the saved archive file and you're there! Review your changes, edit/undo any that you do not want to roll back and you should be set to click "Post" to revert back to that archive!
Remember to archive everything before posting any restorations just in case something funky happens. Always audit your changes too - an advertiser can not audit enough when making a lot of changes via a desktop editor or 3rd party app, in my opinion.
"or import the keywords into a different account?" when you use the editor and import a file (csv or aea), the "upload" of the file is into the editor (not the online interface). so use the desktop editor, import the file, massage the data in the editor, then sync those desired changes / additions to your account.
it's also easy to edit the exported csv format, so you can take an archived, exported csv file, grab the pieces you want, edit those items (like changing the Campaign name), then import them into the editor for the account you want to post them in, check for errors, then slurp it up into your online account (by using the sync feature), and you're running.
okay, that sounds simple - if you work on PPC all the time it is. if you don't, skip the editor - it's like putting a pneumatic jackhammer into the hands of a weekend do-it-your-self type, the hole they accidentally drill will be dug much faster and with more destructive impact. power tools are for carpenters. :-)