So, I've been using WP Glossary on a number of my sites, and it is quite good, for what it does. However, it seems that there are a number of missing features which would take the concept (i.e., a site-specific glossary plugin) and make it a great addition to the WPMU DEV lineup.
WP Glossary is, unfortunately, limited to the site on which it is installed. For most setups, this is probably fine, but MultiSite installs would likely benefit from a central glossary + subsite glossaries setup. This should be relatively easy to achieve with CustomPress.
In essence, what I'm suggesting is the following:
WPMU DEV Glossary
A glossary plugin, based on CustomPress, with built-in WordPress MultiSite support.
A centralized glossary (e.g., glossary.example.com), with a list of terms managed by the super admin or any administrator of the glossary subsite. The subsite could be configured to display both the global glossary and a list of subsite glossaries (e.g., glossary.example.com could be the network glossary, and glossary.example.com/global/ or something similar could be a global list of defined terms across the network).
Independent, subsite glossaries (perhaps with synching support). Each subsite could have its own glossary, which would be a simple list of terms and definitions (i.e., custom post types). The terms could be inserted on a subsite with a [glossary] shortcode, perhaps with a flag for determining if the plugin looks in the network glossary or the local glossary (e.g., type="network / 1" for network glossary terms, with a default of "local / 2"). Synching between subsites could enable collaborative glossary creation (perhaps synching could be configurable to limit which categories sync).
Category support, so that a single site can have one cohesive glossary, but numerous different categories for organization/display purposes (easily achieved with CustomPress). This would likely benefit from integration into the [glossary] shortcode, or, perhaps, a second shortcode for inserting the entire glossary instead of just a term (e.g., [glossary_list] or similar).
In addition to the features mentioned already, supra, the [glossary] shortcode could automatically generate hover text (akin to what WP Glossary does now, though preferably a bit faster than the current Ajax implementation in v3.0). This could be toggled between the full content of the glossary entry and the glossary entry's excerpt (this would be particularly helpful for sites with long glossary entries that still want to have usable hover text).
That seems to be about it for this plugin suggestion. Any comments, tweaks, or other input is, of course, welcome. Oh, and be sure to add your +1!