CalenMob Pro - Google Calendar Client I started off with the free version of this and loved it, so I paid up. This slick calendar can merge your Google and iCal events into one easy to navigate planner. It even supports multiple Google calendars and color coding.

Dropbox HUGE if you're keeping an Android phone and getting an iPad, like I did. My Android is my primary camera, so I have the app on there set to auto upload. On my iPad, I open Dropbox and the photos I took on my Android are right there! I can organize, import into my photo stream, all that fun.

Google Drive If you've been living in Android Land, you know that Google Drive is the green robot's version of iCloud. This is great for any iThing users who don't have a Mac at home for following up on their mobile work. Google Drive ties multiple operating systems together.

Evernote Another classic to link you across systems. Load the desktop component on your PC or Mac, load the app on Android or iThing, and you're synced up! This is one of the first apps I put on my iPad.

Vtok - for GTalk chat, video, free phone calls and texts Google guys and gals love Gchat and Google Voice. This app brings them both beautifully to your iPad and is far, far superior to the "official" Google Voice app which still has yet to be tablet-optimized.