There's a great solution for those who travel a lot or use their iPads in public places - the Security Case and Lock for iPad/iPad 2, which comes with a steel cable that you can attach to an area (say a table leg in a cafe) and then secure the lock-head to the iPad case, making it pretty tough to steal your iPad. Pretty cool and it's just under £60, which is nothing for having some peace of mind.
Another great iPad 2 accessory that we've got is for musicians, speakers or singers - It's a little bit clever - it's called the iKlip. What the iKlip does, is it attaches to a microphone stand, at any height and rotation and allows you to take your iPad onto a stage with you. So if you're a speaker, you can have your notes and control presentations from in front of you on your iPad in a professional manner. Or if you're a musician, you can display your music on your iPad, saving the need for paper (go green!). It's not out yet and the price hasn't been confirmed, but it's a good product to look out for.