I am a newbie to newsgroups and getting free stuff on them. Please tell me the best newsgroups (free or the cheapest) to use and which free newsreaders are the best.
Thanks.
Google Groups is a free web-based newsgroup reader. I am unaware of any newsgroups which cost money to access.
It depends what you’re looking for.
Certain newsreaders are better for text as opposed to binaries as opposed to letting them run in the background downloading stuff. (For what it’s worth, I used to use Free Agent, but it had problems with the later encoding styles, and looking around it doesn’t seem to be available anymore)
For articles, you’ll need to connect to a news server (access is usually included when signing up with your ISP), and you’ll need to download articles in a particular newsgroup. Which group you check is dependant on what the heck it is you’re interested in. Google shows more than 54000 groups available right now, so there’s a bit to choose from.
Like Garfield226 I don’t see how it’s possible to have a group that costs money. It’s certainly possible to charge money for access to a news server. Storing all the daily articles and binary content for 50,000+ groups and allowing all your customers to download from it involves a lot of disk space, bandwidth, and administration for an ISP. Quite often they’ll drop articles after only a few days, or not even have an article in the first place.
Places like Giganews charge a fee for access, for which they keep articles around for much longer, and make sure they have as much content as is available.
Ahem. So if the above doesn’t help you, here’s a list of newsreaders available from TuCows. Get one of them, ask your ISP how to connect to their newsgroup server, and start looking around. 
Briefly:
If you’re interseted only in reading text forums, there are plenty of free web-based newsgroups like the aforementioned Google Groups, among others. There are also plenty of free open Usenet servers that are available for reading in a dedicated news reader. Note however that most open servers won’t allow posting, only reading.
For binaries, you’re going to have to go with a dedicated news reader and a decent news server. Unfortunately, the vast majority of free servers, in addition to not having post access, also won’t carry binary groups. Those that do are typically very slow (little better than dialup if at all). Realistically, if you want binary access with decent speed, good retention (the number of days posts are kept on the server before being expired) and good completion (the percentage of multipart binary posts that show up complete on the server without any missing bits) you’re going to have to pay for a premium server like Deja News, Giganews, Easynews, etc. Few of these are cheap – most cost as much as a cheap ISP account even at discounted long-term package rates. There are some discount Usenet providers out there like Buzzard News, News Demon, ThunderNews, etc., but in many cases you get what you pay for – usually with overall speed.
For a dedicated news reader, the most popular by far is Forte Inc.'s Free Agent. It’s free for the basic version (though you need to upgrade to regular Agent if you want things like yEnc decoding and such) and it works very well – it will automatically find all the parts of a binary post, combine them and decode them in one click, which is probably it’s most useful feature.
To learn more about Usenet in general, including binary posts, newsgroup organisation and so on, see Wikipedia’s Usenet entry.
Since you’re looking for opinions, let’s move this to IMHO.
samclem GQ moderator
Have a look at Slycks’s Guide to the Newsgroups. That should get you up and running.