Whether you have a good reason for wanting to maintain more than one iPhoto library or your collection simply became un-browsable long ago, Brian Webster's iPhoto Library Manager is your answer. This slick little utility was mentioned briefly in an Ask TUAW back in May, but to summarize: iPhoto Library Manager makes it painfully simple to create multiple iPhoto libraries, keep them anywhere you want, automate them with AppleScript and Automator, switch between them with a single click and even set one library as the default. But it doesn't stop there - the features I've already listed are available in a free version, but registered users get to enjoy the ability to create library shortcuts for opening straight from the Finder, copying photos (and preserving all their metadata) between libraries, merging libraries and copying photos from multiple libraries into a folder for synching with an iPod. To top all this off, the new v3.3 brings iPhoto '08 compatibility and some other goodies.
What does it cost for this multiple iPhoto library goodness? To gain the more powerful features and give Webster his due, iPhoto Library Manager costs a mere $19.95 from Fat Cat Software.