A colleague recently pointed me to RTG Timer and RTG Bills. RTG Timer is an online timekeeping solution that integrates with RTG Bills, a Windows-only billing software. RTG Timer is online, so it is platform-independent. At $95/license, RTB Bills is a pretty hefty price for what looks like a fairly simple piece of software–at least compared cheaper practice management software. But then again, it is less expensive than time and billing solutions from bigger companies.
Might be worth a look.