Advice on Archiving large iPhoto Library

My meagre 250Gb Hard drive is close to bursting.
Photos aren't my income, but I do take a lot of them and they are important.
Suggestions welcome as to how to set up an external archive.

I'd like to access these easily (either direct or through Airport Extreme)

Do I need to partition discs to organise?
I've looked at iPhoto Library manager
Carbon Copy Clone

Areas I am fearful of -
losing tag data
setting up something complicated which won't 'flow'

[I should add that I have a 500gb portable HD on stand by to take the strain off the iMac so I can continue to work.
An interim solution would be appreciated]

Your help/advise/wisdom appreciated

FYI
I'm currently looking at Old Toad's Tutorials (http://toadstutorials.info/)
23- Creating and Using a “Referenced” iPhoto Library
and I'm getting a little dizzy...

aristobrat said:

If you have an iMac, and the external drive will always be connected, I'd personally just move the entire iPhoto Library from your iMac's internal drive over to the external drive. That would free up the space on the internal drive. I'd also pick up a second external drive (at some point) and setup Time Machine to backup both your internal drive and external drive, so if anything happens, you'll have a copy of data from both drives.

Click to expand...

Thanks for the reply.
If I understand you're point correctly, TM has the ability to allow me to back up from one external HD to another?
How do I do that?

So, the way I've cracked this (in my own mind anyway) is to use Carbon Copy Cloner to make a disk image of the whole iMac on an external 500Gb hard drive for the moment.
I will free up space from my iMac bit by bit.
I'll look to get an external HD to keep tethered to the iMac to build up the photo library and this other to make incremental TM back ups of both.
Let me know if that's twisted.