The techniques to choose depends somewhat on how far along you are in building said website. For early stages usability testing with paper prototypes as you go along is a quick and inexpensive method to catch errors. It helps a lot in designing test scenarios, if you have good idea what users come to your site for.
Another good method early on is card sorting to find out your users mental models about the sites information architecture. In essence you write content to cards and have a bunch of users to sort those content pieces to groups and then name the groups. If you are tight on resources, I would recommend doing this with a remote web tool, like OptimalSort or WebSort.
Card sorting is also fine for later stages. For checking usability on finished sites, basic usability testing as you suggested would be fine. In general considering generally scarce resources, you are better of doing qualitative usability testing, which in general requires less users. However as with all usability testing and user centered design, you are better of if you can do the testing iteratively. Ie. a new round of tests after fixing the biggest problems previous round found.
I would also recommend having a few people inspect the site with the help of heuristics. One commonly used set of heuristics is Jakob Nielsen's. Do note that modifying the heuristics to your site's domain is likely to improve the results.
If you want to know more about usability and usability testing, I would recommend Steve Krug's books:
Both books are very easy reads and most importantly very short. Even slow reader can finish either in one sitting.