LiveTime is probably the most common for club or major event racing. A full suite of options. But it has a monthly fee. Probably not an issue if you are running a public track.

At the track I have at home I use NextLevelTiming. It’s free, but you can get a Pro version for $25/year that adds some extra features. It is fine for running a single race or practice. But, it won’t do things like seeding multiple heats or determining top qualifiers, so it’s probably not ideal for larger club events.