This is a good time to mention my new strategy with my Kindle Library, which (as most of you know) is so large it causes all the Kindle 3's on the account to constantly reboot, if wireless is left on (apparently only in WiFi areas, from my experimentation). I have set up second account (some of you may want more than one) and I am "repurchasing" all the zero cost books there, as they pop back up as repeats, and deleting them from my main account. You might even want one for "free - indie author" and "free - commercial publisher", although I don't think I'll go that far. Those with kids may want to set up a separate account just for their books, as that is the best parental control method I've seen for Kindle - only have kids books in that account (paid or free, since there aren't that many free books in this category, from what I've seen).
It'll take a while to fix my main account, to be sure (it appears I need to get to around 3,000 books or less to fix both the rebooting issue and the inability to access the full archive from my Kindle). Another thing I'm doing to get there faster is that I've backed up all my Kindles to my hard drive, then imported all the AZW books into Calibre (using a new, labeled Library for this purpose). I then set it to convert to MOBI - those with DRM will fail, those without will succeed; I then deleted (from Calibre only) those that ended up without MOBI editions - what's left is all DRM-free books, which I'm removing, a few at a time, from my main Kindle account (to make it go faster, open up several tabs on your library - delete a book, switch to another tab while it refreshes).
Amazon lets you move your Kindle freely between accounts - you first deregister from the account it is on, then register to the new account. Make sure you do this with a wireless connection on - you Kindle must see that it has been deregistered or it won't properly register to the new account. It is often easiest to do this from the Kindle itself (at least, with a K3 or the Touch). Nothing gets wiped from the Kindle when you do this (unlike the nook tablets, which must be wiped clean to change accounts), so you can move your Kindle, grab a book or two, then move back to the "default" account. While you have no physical Kindles attached to an account, purchases just go to the CloudReader, so you don't even have to worry about this process when buying from the web. To make it easier for me to remember which account I'm buying in, I use two different browsers, with my default browser on my main account and a second browser (Chrome, in my case) logged into my "free books" account and that account has no payment methods, so it can't buy something by mistake (the only downside is that I can't add free pre-orders on this account, until they actually release).
You can also register your Kindle to the account from the web page - this is handy if you just want to download a book to your computer and transfer via USB (emailing might work, since it will have that Kindle's serial number in the DRM, but I haven't tested this yet). You do still have to deregister from the first account to start (it won't let a Kindle be registered to two accounts at once), but you can cut/paste the serial number from the first Manage Your Kindle Page and the entire process of de-register/register to 2nd account/send book/deregister/register to 1st account only takes about 1-2 minutes, with two browsers and a bit of practice. Amazon remembers all your settings for email and Kindle name on the first account and I haven't seen that this even impacts subscriptions (although all I have are a few blogs).