Not to be disrespectful, but all of the plug-ins are just kind of thrown in a "pile". A rating system would be good. It may not be perfect, but I usually find that a system that identifies trends helps me personally find things that are more useful to me. Maybe add the option to list by Name, Date, Rating, Author, # of times downloaded, etc...you get the idea. I don't think that using tags is very helpful, at least not to me. I only signed up today, but I have been using this site for a few days. I decided that I really like GIMP and find it to be an excellent alternative to Photoshop. Not to mention I like the mentality behind open source software. I actually read the entire Photoshop CS4 EULA, and they just go on and on about what you can't do with their software. I don't know how to express in words my dislike of the mentality behind things like that. Anyway, I kind of deviated from organization, but I would like to see a little more professionalism behind this site. It has a great idea, its just when a person like me who just started using Gimp and is unfamiliar with this site comes to it, it is a bit much. Some people here are probably familiar with most of the content here and can keep up with it, but to me its an avalanche of filters that I have to sort through to find what is useful.
I know what I propose will be a bit more difficult that what Ingo has suggested, but I'm sure there are plenty of competent people around here capable of making the change. Another idea, instead of listing the filters/plugins on the left followed by tags in the middle, I would suggest replacing the tags with a small description of the filter in question. There is a lot of prime screen real estate that is simply wasted on the same words over and over again, and to get a description of the filter, I have to physically follow a link to another page to see it. It would save me quite a bit of time if I were able to browse through all descriptions at once, and like I said, listing the tags is just a waste of valuable screen space anyway. Presumably you would know what the tags were anyway because you searched for them (I know this is untrue in some instances but I am just trying to point out the flaws in this system). If this is something that seems feasible to the developer of this site, I would be glad to offer any assistance I can. In fact, I would be glad to offer assistance in any needed area. It's something to think about, and surely you all can see the flaws in the current design. I would argue that there is also no need to list the file name where it is currently listed. Since one is required to follow a link to the download page for every filter anyway, it would seem that said download page would be a more logical place to show the file name.
One more suggestion. I think a "Home" section should be added to the links at the top right. After a person leaves the initial site "http://registry.gimp.org/" the only way to get back is to use the navigation toolbar. A link to that page would be a simple and quick way to get back to the beginning (Sorry if it already exists, but I don't see it anywhere). The logical place would be at the top right with the rest of the links.
Anyway, Thanks for reading my suggestions (unless you didn't. In that case disregard my thanks until you do)