Timer-7 is a free computer time clock. This free edition (as there is also a pro one) will let you set a timer, but unfortunately, just one at a time. You can use it as an alarm to turn off the dish you're cooking, to see how fast you can do a test in the process of learning, not to forget to take a break, to clock some tasks or just whatever you want.
When the time is up, the reminder will pop up at the bottom right corner of the screen. That is not so convenient as you can be not in front of your computer to notice that. The program offers you to play a .wav file you've chosen as a signal to remind that the time is out, but again, it can be useless if you've forgotten to unplug your headphones, for example, besides WAV is becoming less and less popular, so not everyone will find any tunes in that format on their computers.
The interface of the program is rather user friendly, as you would expect from an alarm clock application. I can't say anything about its design though, as is just as simple as possible.
The pro version of the application costs 12.95 dollars, you can buy it from within the utility by clicking on the “Upgrade to Pro version” button. The pro version will let you set more than one timer, to specify primary and secondary clock alarms and save and load various functions.