I've just created a free version of my RoomCalendar.co.uk guesthouse availability calendar web application.
Hopefully I'll get some people using it - giving it more exposure.
Although limited, it does still retain nice features like an attractive, concise report which guests can use to check the guesthouse availability and is interactive - allowing guests to choose their own date rate. It also still has the nice point and click calendar which makes updating booked dates quick and simple.
If you have a guesthouse, B&B, boutique hotel, self-catering accommodation, function room or such like which you rent out - you could be showing your availability in minutes on your website - giving you guests a slick, interactive tool to check availability - improving the user experience of your website - and all for FREE!