Colloquy [http://colloquy.info/] works well for IRC. Doesn't do IM though.

As one of the colloquy devs, I must step in with the more useful nightlies link: http://colloquy.info/downloads/nightlies/ :)

I believe the adium team is hard at work on IRC for either the 1.4 or 1.5 release. Not helpful right now, but just a heads up.

Mibbit. If you need a desktop solution, then use Fluid to turn it into an SSB.

We're forced to regularly ban Mibbit users on Freenode technical channels due to abuse masked by Mibbit's proxying, and for that reason I must say I'm not a fan.

That's the double edge that comes from any ease of access. Mibbit makes IRC very simple and very easy, and so more people use it, and with people come trolls.

That said, if you're looking to access IRC easily, that's the way to go.

It would be quite easy for axod to pass along user's IP to the server instead of masking it through Mibbit. Having the user's IP as their realname isn't a real fix..

No offense, but mibbit is for idiots.

Use irssi or xchat.

Give me a fucking break. It's a method of connecting to IRC. To the best of my knowledge, the various programs don't bestow special powers on people. They let you type lines of text and post them to a live room. Occasionally they let you format messages.

How is Mibbit for idiots? It lets me give URLs to people who want to join chat rooms, so if I want to invite somebody to a channel I don't have to say "Download this, then fill out this and this and this in the boxes," I can just link them and they click it and they're in. I can style it to my heart's desire. It's customizable as anything. It supports tabs for multiple rooms at once.

I use mibbit all the time when I'm behind a firewall that blocks IRC traffic. I don't consider myself an idiot. It's probably also a great option for thin clients.

I do use Colloquy or irssi when at home, though.