It's rare to find a one word domain name website for sale at a decent price. Right now at DNForums, Skirts.org is for sale with a starting bid of $3000, and a current Private Bid of $7000. It's running an Amazon affiliate script and making about $60 per month, but has the potential to make much more than that with such a marketable top level domain as this.
PHP License Script is a unique custom coded script that allows php programmers to resell scripts, while protecting their property. It includes the rights to the script and the site. It currently sells for $50. Monthly revenue is about $475/month, but it has only reached that level one month. The bid starts at $1000 and Buy It Now is set at $4500, but may go down depending on buyer interest. Anytime one can pick up a custom property like this should act quick. Available at Sitepoint.
Twitter sites for sale is nothing new, and the concept of twitter signatures isn't new. Twitter signatures are just Twitter banners that update with your twitter posts, but these are sites that can generate traffic and are easy to resale. I've personally flipped a twitter signature site in less than a week and pocketed an easy $325. What attracts me to this site is the domain Twittersignatures.com. It's perfect, and the website design is really good also, fitting in with the Twitter style. This will go fast so pick it up over at Digital Point.
What makes The Virtual Real Estate Game stick out past other websites for sale is its professional look and high quality idea. The idea is simple: people pay to buy and sell virtual real estate within the game, and can resell their properties amongst each other as markets swing. The site cost over $10,000 to develop. What you are buying is a one site license to use the script, promote the game, and make money. You sell virtual upgrades within the game. The site is currently for sale starting at $1500 on Sitepoint.
A new concept that I would like to see implemented more often in websites are ones that are targeted to a female audience. This site, CuteWordpressThemes.com is a great example of a website that hits a good target niche market with a high quality product. This site for sale has a great design and 4 custom wordpress themes bundled as a package, plus one free template as a bonus. The site starts at $250 with Buy It Now at $847 at Sitepoint. I believe $500 is a good price. Any higher can be outsourced for cheaper at the same quality.