The Inner Ring site has produced an excellent calendar that you can import into a number of different calendar programs, including Google and iCal. It includes some of the second tier races as well as the classics and grand tours.
inrng : downloadable race calendar
For Apple, use "Save As" on the link and then tell your computer not to append a .txt to the filename. At least on my computer, it wanted to change the calendar to a text file even when I simply downloaded it straight onto my computer.
Also, if you have iCloud, you can put the calendar on iCloud instead of having to copy onto each computer or device. Select File>New Calendar>iCloud and then give the calendar the name you want. Then select File>Import>Import and show iCal where the saved .ics file is and then to import that file into the new iCloud calendar that you just created. Give it a few minutes to sync up, and then you should be able to see the calendar on your iMac, iPhone, iPad, iThis, iThat, as long as they are all connected to the same iCloud account. You'll never be without.
I searched but did not find any stipulation about copyright, so I don't think posting this here is a violation. But if the moderators feel otherwise, I defer to their good judgement!