AppColl is very good. I used it for about a year and was pretty happy with it. It is web based and therefore platform independent (i.e. works with Mac, PC, or Linux). Easy to use and easy to customize. I think they charge about $100/month. Their support is excellent.
If you are a Mac, and want to use something local, you can also use Market Circle Daylight and configure it to be a docketing system. That is what I am using right now and am pretty happy with it.
Hope this helps,