Forum plugin bbPress 2.0 is soon to be released, and I expect that many extra plugins will be coming to expand the forums. So, on Dev4Press, here is the first our bbPress expansion to add attachments uploads capabilities to topics and replies. Plugin is available for free.
Plugin is very simple to set up and use, and this will make easier later to expand it with more features if needed. Plugin will add Attachments panel in the Forum administration menu where you can set basic settings. All the settings can be overridden for the individual forums via meta box on the forum edit panel.
Topics and replies panels on the admin side are expanded with columns with attachments count. And the admin editors for topics and replies have meta box with list of attachments.
Based on the settings, plugin will add attachment block into the topic and reply forms. Once the topic or reply is saved, plugin will check each attachment and if they are OK, they will be saved in WordPress media library and attached to the topic or forum. And, they will be listed and linked in the topic or reply. Uploading of files is handled by the WordPress built-in functions.
You can download plugin from Dev4Press or from WordPress.org. You have links bellow. If you have any suggestions or bugs to report, you can use comments or the forum.
GD bbPress Attachments Home Page
GD bbPress Attachments on WordPress.org