What's the easiest way to free up disk space on my iMac with a huge photo library? This is a hybrid hardware/software question with a few more factors than the typical "freeing disk space" question.

I have an older iMac with (I think) about a 250 GB hard drive. It's been running out of disk space for a while, and each time I find some way to recover a bit more room. I've used DaisyDisk, etc. to identify large unused files, moved my iPhone/iPad backups to cloud, etc.

At this point there's just one big culprit left: our iPhoto library, which has been fed increasingly large photos. (iPhone 4S + Nikon DSLR -> way more megapixels than my earliest photos!) The iPhoto library hogs most of the space now and I'd like to avoid one-by-one reviewing &amp; deleting photos if I can help it.

Is there a software solution? Can I tell iPhoto to archive the oldest photos to a NAS? (I have plenty of network space) And if I do that, will photos take longer to open?

Is there a hardware solution? For instance, if I buy a Time Capsule is there a one-step way to relocate my existing photo library? And again, will it slow down the use of photos on my machine and/or prevent me from seeing all of my albums?

Also, I'd like to start moving some of my music back to the iMac - any solution that will let me do the same for iTunes (keep some local, move some to network storage) would be appreciated.
Assuming your NAS is always available and connected to your iMac, you can move both iPhoto and iTunes libraries to the NAS and use


symbolic links from ~/Pictures and ~/Music to fool the applications 
start the application with Option pressed to select the alternative location
iTunes: select alternative storage location in Options 
iPhoto: start by double-clicking moved library file