More solutions:
For a hardware solution (if wanted) the Camera Connection Kit will let you plug your iPhone into the iPad and import the camera roll.
PhotoSync is a handy app for direct bluetooth photo copying between the computer, iPad, and iPhone. It's a universal app, so you only need to buy it once, though you do need to install it on both devices. {there are actually two apps named PhotoSync. I use the one without the space between the words.}
I like the new PhotoStream service that works with iCloud, but it can take a while to transfer photos, so if you need something 'now' the above solutions work well. The DropBox (or other cloud file solutions) take a little longer (mostly from all back and forth needed), but are still faster than PhotoStream; at least on my admittedly less than great internet connection.