Starting with the last question first - CD's are probably the way to go for backups of important documents etc. I wouldn't imagine that Yahoo would offer anything significant for storage for free!
As for "freebies" and almost free - really depends a lot on what he's going to be doing and how he has set up his iMac. If he has it partitioned and wants to use a partition as backup, Carbon Copy Cloner is a nice little $5 shareware app that I wouldn't be without.
I'd also have him download Mozilla Firebird, on the browser front.
I don't have a lot of freeware - though a brief perusal of VersionTracker's 21 pages or so of OS X freeware certainly yields a lot of interesting possibilities...if only I had the time to check 'em all out!
On the shareware front, most of what I have I've got because I find it indispensable for what I'm doing - but others wouldn't find it useful at all. For FTP, I use Transmit, for scanning with my older SCSI scanner, I use VueScan, I used to have BBEdit Lite, but now have the full version...I have WeatherPop which is a free little app that tells me the current weather conditions here up in my menu bar. I do have URL Manager Pro (earlier version) which I have the best of intentions of someday actually USING, but again - I rattle along with little time for housecleaning - virtual or real!!!
