I almost always go through the process of creating a prototype for sites that I build. They vary in execution from simple line-drawings on paper to partially working applications, and eventually they are used in usability testing with individuals who match the target audience of the site. As well as extremely useful for usability testing, the prototyping process really helps flush out issues with functionality and design in a very tangible way.
The most important pages of the site are arguably the map detail pages, and last week I finally got the prototype of these pages to a point where I think it's nearly perfect. A major milestone that seemed to have taken months to reach, but well worth the effort — I was never really happy with the current version of the map detail pages, which started out in a questionable state and ended up having things "duct-taped" to the page over time.
The entire site is under examination to be sure, but I'm also focusing heavily on the map browsing section. Sometimes you're just in the mood for a new map but not sure exactly what and having the ability to peruse the map database is handy (not to mention good for search engine spiders). The current iteration works, but is slow and offers no real filtering mechaism while you surf — forcing you to page through all of the thousands of maps in the database.
Browse has gotten a major overhaul in functionality and interface-design to say the least, and I imagine that with the changes it will end up being as useful as (or maybe even more than) the ever-popular search.
There's a number of things left to prototype (the map submission process will probably be my next big hurdle), but I'm guestimating that I'm somewhere around 50% complete. Once finished, I'll begin soliciting feedback and testing from a select few users of the site.