I had the same requirements. First tried SugarCRM, but found too many bugs. Then switched to vtiger. vtiger uses the same engine as SugarCRM, but its interface and features are much easier to get used to.

I am extremely pleased with vtiger. vtiger is 100% open source and free (as in free beer), all you need is a server running Linux or Windows with a recent php and mysql version installed. Just dump the files to your server, follow the instructions and get full web access.

You can access their live demo here (admin/admin).

The problem of all these software is that the ruler follows the mouse. Much more useful would be that the ruler automatically detects the next line to read and jumps there when the user hits a key. This should be fairly easy to program by looking at the few pixels below the current line. Now that would be very useful.

A challenge would be to stay on the same line even when scrolling down the current page (or hitting page down). By the way, this is the thing that I find most challenging: after hitting page-down, find where was the last line I was reading before pressing the page down. A software automating this would be a great productivity tool.

I am sure that there are many excellent programmers here that would be willing to take up the challenge...