What features does a time tracking system need so developers actually log their time?
In our case we are a 30+ person custom development shop, looking to replace an aged custom solution. Key business need is billing for our consultant's time. Ideally the system would help us figure out if we can complete the project(s) on time and within budget.
Related question: How Do You Track Your Time
I found SlimTimer to be the least intrusive, yet most-likely-to-garner-somewhat-accurate-results application.
SlimTimer is good. (It's owner started UserVoice, which StackOverflow also uses).
Feature number 1: It needs to work painlessly. Brief digression, our in-house time-keeping app is deployed via click-once, but it has fatal conflicts with assemblies that we develop in house and that are stored in the GAC on developers machines. Net-net, it hasn't worked for me in weeks and I have no motivation to resolve the conflicts because it all it does otherwise is take away from my development time.
Every few months, the VP of development has a crackdown on the lack of people keeping up to date, and we all run some script to fill in bogus details for the last few months.
Maybe I should put a timer on my office whiteboard "Number of days since keeptime worked..."
We use the Jira application from Atlassian for Bug/Task management and it has pretty good time tracking features.
It also has some really nice integration features to your source control system so every can see who is working on what, how long it has taken and which modules were updated.
I use FogBugz. As well as time tracking, it's got great project planning and estimation features based on a statistical analysis of previous estimates. And it's easy to use.
TimeSnapper. It's awesome. It lets me see what I've REALLY been doing throughout the day. I suggest giving it a try.
No matter what system you use, developers won't log their time unless they have no choice. Our developers have gotten a lot better at it since our management has a query that will ping everyone who didn't put their time in the day before. Daily input is a must. Even doing manual timesheets as I did for a government contractor, we were required to do them daily and have them availble at all times for surprise inspections (which were done frequently).
We use a system called Intervals that has increased our billable hours considerably. The reason for this is that it has multiple timers that operate like a stopwatch. We simply start and stop timers as we tackle each task throughout the day. By the end of the day we've tracked all of our time rather efficiently.