Visitor Statistics
Obviously you will want to know how popular your site is. Who is visiting it, how often, how are they finding you, how long do they stay, what are the most popular pages etc.
There are a number of statistics packages in the market, but I generally stick to two. These being Statcounter, a highly configurable, rich, award winning and free service or Google Analytics; equally free but perhaps less user friendly. Statcounter has the usability edge in that you can easily login to the system yourself and check all your statistics on-line in real time.
Both these packages will give you a mine of information upon which you can make decisions about changes or additions to your website and your marketing.