Hey now I said if you own a PC you shouldn't be without one of these. You already have one for your Amiga so you are set..
As far as IRC clones my favorite is still MIRC, but I use a messenger called Trillian that incorporates, Yahoo!, MSN messenger, AIM, IRC all into one program (not into multiple IM clients) and it's IRC program is pretty decent too, I use it routinely to visit #AROS.
I put open office on the list because it's a killer app that basically open sources an office suite and well honestly it's better than it's Amiga equivalent "Gold Disk Office" and honestly gives Microsoft a lot to think about..
I wish someone would port Open Office to Amiga Classic, AmigaOne, MorphOS, and Aros.. That would give the platform a really top notch and free productivity suite that's popular with Linux and Windows users alike. Mostly because it's free and it's on par and file compatible with M$-Office..