Well, there are several other ways to get manga or anime other than using IRC. So I decided to mention them briefely here, tho I highly reccomend going to IRC first.

Edonkey/Emule/Overnet are all basically the same thing, they are different software programs that are all used to access the same P2P network. Basically you download and install the software, then go to various websites and click on links that start with "ed2k://" instead of "http://" and those links are added to your download queue in the edonkey/emule program. It downloads the file from anyone that is sharing it and then shares it off your computer as well. There is actually alot more to it than that.

Go to these sites for more information:
What Is Edonkey
Get The EDonkey2000 Program
Get The EMule Program
Get The EMule Plus Program (Reccommended)

There are a few Beginners Guides - HERE, and HERE.

As I said before, there are a whole bunch of websites where you can find edonkey links to click on. Such as Noated's File Depot, and the biggest is MangaReactor.

Another way (other than using IRC) to get manga is using a P2P program called Bittorrent.

Basically bittorrent is a very small program that you install on your computer, then you goto a website where you click on a link that looks like this "http://url/file.zip.torrent" it then opens up bittorent and downloads that file from anyone sharing it. It shares it from your computer as it downloads it from others and continues to share it until you close the bittorrent window.

Here's a complete Bittorrent FAQ that will answer all your questions and also has the program for download. Or you can download the origional bittorrent program from here.

And here are a few of the best places to find bittorrent links to click on: Noated's File Depot, and the biggest is AnimeSuki.