Smart Cover? YES!
Case? Highly reconmmended...I went the cheap route at first waiting to see what other products came out. I Still have, and love, my cheap initial purchase...a zippered travel sleeve made by STN purchased at Staples for less than $20! Take your time selecting your "final" case...go cheap at first then look around.
Camera Connection Kit? YES!
Keynote (App, $9.95)? YES! ...you'll wonder how you ever lived without it
Pages (App, $9.95)? YES!
Apple Bluetooth Wireless Keyboard...if you plan to do a lot of writing. I didn't plan on it at first but seem to be doing more and more since I got "Pages" and my keyboard. If you are going to get a keyboard I highly recommend the Apple version. Sure there are others...some folding...some built within an iPad case...etc...but none as well built, light weight and perfect size as the Apple. Personal opinion, of course!
Good luck,
BJ