You've already seen both Kiteman's and Noah's responses. Here's another from a non-staff member.

1) Nested categories are difficult to manage or navigate. It eventually develops into an N² problem for everyone. What we do have are "tags", which you can use to provide more refined categorization.

2) As Noah implied, the in-house search interface is crap (I'm not staff, so I can say that :-). You are much better off simply using Google: after your search words, put site:instructables.com" and it will limit the search to things here.

3) Noah :-)

I'm an admin and I just read your post. My responses are similar to Kiteman's, who is kind of like an honorary admin since he's been helping us out with the site for so long. You're totally right - we've got lots of categories as it is. If we add in any more, which we're trying not to, they'll likely come as sub-categories. Also, our in house search has some serious problems. It's too effective really, returning any and all mentions of your search query, and not limiting it to what's relevant. If you want to then sort your search results, as you said, you get some bad results. This is a logged and known bug that we've got in the queue to get fixed. Thanks for your feedback - we're listening!

1. No matter how you subdivide the categories, there will always be projects that don't fit, or fit more than one.

2. Once you have searched, the tabs at the top of the screen allow you to narrow the search the way you suggest.

3. I read it, and the statistics box to the right says that two others have as well. Somebody from the admins reads all the feedback posted (that's what the feedback forums are for), even if they don't actually reply to the topic itself.