Zoho launches Discussions: free and easy forum software
The basic service is free and lets you create up to 2 forums and 2 sub forums. You also get 100MB for file attachments (like pictures uploaded by users). You can also pay $25 to $75 a month for more storage space and the ability to create and manage more forums.
Advanced users may find Zoho Discussions a bit limiting. You don't get nearly as much control as you would using a self-hosted forum package like vBulletin, phpBB, or Simple Machines Forum. But there's a lot to be said for quick and easy. And as an added bonus, hosting your forum on a third party site like Zoho makes it a lot harder for users to hack your primary web page by uploading shady file attachments.
Zoho Dicussions also has a few nice features that you won't find in all forum software including the ability to bookmark a topic, add tags to a topic, or subscribe to the RSS feed for a forum.