These are for Android:
Save My Attach: Allows you to save attachments from emails to SD card.
GMail Attachment Download: Same as above, sometimes a little more versatile.
Barcode Scanner: scan barcodes of products when you are at stores, see if you are getting ripped off, possibly get them to price match. Also scans QR codes such as what you see as my Avatar.
Cloudlist: Create shopping, to do, and other lists, share them real-time with wife, as you check items off the list they get checked off her list, vice-versa.
ConvertPad: Convert between units of measurement. I use this a lot for 4x4 stuff.
CraigsNotifica: Updates you when stuff you are looking for on Craiglist is advertised. Updates happen almost instantly. I have been the first call on several items using this and got them as a result.
Dropbox: Access all your files from anywhere, they get updated at all locations. Can also share folders with wife / coworkers. I pay $100/yr for additional space and it is worth every penny.
FoxFi: Free wifi hotspot using your data plan, does not require root or monthly plan from service provider. I use this constantly. Turns your phone into a wifi router.
Package Buddy: Track any number of packages from any number of shippers. Updates you as packages get updates.
Printershare: Print documents from your phone to any wifi printer.
Torque: OBD2 scan tool for cars. Has most of the same features as a $1200 scanner for $2. Read and delete codes. Works via $30 bluetooth OBD2 dongle on eBay.
Voicememo: Record your voice to make mental notes. I also plan to use this if/when I am pulled over by a cop.
I'll put a gratuitous ad in here too since my brother and I developed and own this app:
Flashy Tunes: Keep your young child entertained with music and flashing lights. My 6-month old will stare at this for hours at a time if I let her.
J. J.