I admittedly dont know much about usenets or newsgroups. What Im looking for is an online usenet to search for groups. I’m aware of Google’s groups, but are there any others?
There aren’t seperate usenets. There’s just Usenet. Google Groups carries everything, except for binary groups, which are really only good for porn and commercial software.
Like friedo says, Usenet is a single thing. It’s a distributed discussion board.
Like the web, and like email, it’s a technical infrastructure designed to serve a specific purpose. The Usenet network consists of a large number of interconnected servers, called news servers. Together they manage a pool of newsgroups, named discussion forums where users posts messages. The way this infrastructure works, when someone posts a message to one server, that server forwards the message to other servers so that, eventually, all servers contain a copy of the message. This means that when a user on server A posts a message, a user on server B might not see it until several hours later, at the worst.
Usenet, then, is a formalized network of such news servers, and afaik it’s the only one in existence. (It’s perfectly possible to run a private news server, though; some companies run servers for internal communication within a company.)
On Usenet, there is a formal hierarchy of newsgroups (comp., rec. etc.), and newsgroups are created (or deleted) by a voting process. There’s also an unmoderated space, the alt.* hierarchy. Some groups are moderated, where all messages are filtered through a pool of administrators, ensuring an optimal signal-to-noise ratio. Most groups are unmoderated, but they’re still subject to spoken and unspoken rules and etiquette.
To answer your specific question: Google indexes the Usenet newsgroups and adds a web interface to let you read and post messages. (Traditionally, you use special clients, such as Thunderbird, to access news servers. Note that most news servers are only open to customers of specific ISPs; if you want to use such a client, you should ask your ISP if they have a news server for you to use.) There are other search engines that index news, AlltheWeb being one. There are others.
Reading a bit about the Usenet organization and rules is a good idea, as is reading the rules and FAQs of the newsgroup you want to participate in. Usenet started out as a great place to talk to like-minded people. The last few years, starting with the onslaught of AOL users, has been slowly suffocating under the weight of moronic users and spam; personally I don’t read news anymore and stick to mailing lists.