I cannot say this enough—I LOVE my iPhone. Back in June, I decided that it was absolutely necessary to have a business line, as my personal cell phone just wasn't cutting it—and I was getting sick of paying overage charges for long client calls. Then fate stepped in, Apple dropped their price on the 3G, and I had a phone that could field calls, check email, and entertain me on the occasional ferry ride into the city.
FlickrA great place to upload your photos and to check out some really great images.
Photoshop.com MobileEdit and share your photos.
RunKeeperWhile technically not a design application, I love this because it tracks my runs—pace, route and mileage... 'cause running brings me sanity (and gets me away from the computer)
MintKeep track of all of your finances in one place.
SkypeMake a call to anyone with an account... for free. Amazing.

myPANTONEPANTONE color libraries on the go
Best CameraAnother way to edit/share your photos... this one with cool filters.
The Typography ManualLOTS about type.
PalettesThe name kinda says it all.
Etsy AddictBecause that's what I am.