Here are some tools that have been useful for my training and racing.
Enter your most recent race result and it will calculate very helpful information for you. It’ll return potential performance equivalents and training paces based on your most recent race. For example, my most recent Half Marathon time of 1:25:10 gives me a potential Marathon time of 2:59:37 with the pace of 6:52 min/mile (4:16 min/km) on a similar course and in similar physical and running conditions. How accurate is this? I don’t know…, but it is a good indication for upcoming races and a good planning tool for them. The training paces are broken down to long runs, easy runs, tempo runs, etc., and help you design or tweak your everyday training program.
If you have a heart rate monitor you can strap it around your chest on your next 10K or Half Marathon race, that’s great. You should use the reading from the heart rate monitor to know your Maximum Heart Rate (MHR). But if you don’t, this is a useful tool. Scroll down to MHR Calculator and enter your age to get your MHR. I know there are different methods but any one of the estimates is within a few beats per minute from others, so use one you like. Then use the estimate to get your VO2Max. Obviously, there will be differences depending on your fitness level. For example, my peak heart rate reading from my recent Half Marathon was 188 and the estimate from this tool is 178 (Combined Londeree, Moeschberger and Miller method).
Cannot find your past race results? Athlinks.com is likely to have them. Need to open a free account to access to their database but worth it.