I've had very good service from
http://www.newscene.com/ They offer month to month at US$13/mo.
I spent a considerable amount of time experimenting with free news feeds. For me the time involved in keeping an eye on them and then searching for new ones when the one you are using decides to go off line for a week or two at time, was a pain and cost me way more than $13/mo.
On top of that Newscene knows that I'm pulling news for vBulliten and they said no problem and that they would work with me on spam issues that may arise. So far I have not allowed posting from our BBS to Usenet, I was waiting on the moderated usenet post fix from Paul. Health issues kept me from updating till now. I'm planning to upgrade to the latest unsent hack this weekend.
I'll keep everyone informed if I run into any posting problems with Newscene.com
Cheers!