Couldn't see any info here on how to do this so here's a guide I did for someone a while ago. Due to the problems with P2P software it's worth checking them out.
1. Get hold of some decent newsreader software e.g. Grabit over at
www.shemes.com - I'll use this for the rest of the instructions as its easy to use and does the job well.
2. install the software - it will ask for your ISPs news-server. this is usually of the form news.PROVIDER.NAME e.g. news.ntlworld.com
3. you then need to download a list of the groups your ISP provides so download the grouplist. Wait for a while......
4. when the list of groups appears select the ones you are interested in e.g. alt.binaries.dreamcast and 'subscribe' to them. (Double click on the name in grabit)
5. You then need to download the headers of the messages in the groups you are subscribed to so find and click the appropriate button e.g. Update groups. Then wait for the headers to download.
6. Looking at the headers you'll see lots of things that may interest you so just double click on them to download or draw a multiple selection box and right click and "Grab selected articles". In grabit the headers are colour coded so that if the text is in black the complete set of messages is there. Hovering over the header will tell you the size of the file.
7. Go to where the messages have been downloaded and you should find a series of messages/rar files. In grabit they are stored under the the program directory in a sub-directory called the name of the group.
8. If you have downloaded rar/zip files then you will need to uncompress them before going any further.
Another thing people might like to know is that headers that contain files with the suffix are PAR, P01 etc. are parity files and can be used to reconstruct missing parts of files. This requires a utility like fsraid
www.FluidStudios.com Recently files have been posted using PAR2 parity files which require a utilty like Quickpar
http://www.pbclements.co.uk/QuickPar/ to repair. PAR2 is better in that it uses block based calculations for the parity and so only requires a number of block files equal to the missing/corrupt files to fix. PAR1 replaces the whole file and so you needed a complete PAR file to replace a missing/corrupt file. PAR2 takes a lot longer to repair however.
Any files you download of course will need to be burnt to a disc using the correct program - Disc Juggler for .CDI while Nero is good for .NRG.
A good place to find what is available in the newsgroups is:
http://www.newzbin.com/Not all ISPs cover all newsgroups and have different article retention rates so you can pay for a decent service with something like easynews or use a free news service like biggulp.readfreenews.net but be aware this limits your download speed to about 4k (but is useful if you have any missing parts).
If you want to start posting files then there is a useful guide on shemes.com about using powerpost.