Olymon was a program between 2000 and 2010 run by Professor Ed Barbeau from the University of Toronto. He would publish monthly problem sets, and students could send in their solutions to receive feedback. The problems and solutions are preserved here, and are excellent training materials.
Tips
Writing up solutions: this document should be read by any student studying for math contests. The information in the section "Olymon and the Olympiads" is outdated and no longer accurate.
French translation (courtesy of Jean-David Houle)
Problems
There were 691 total problems published in Olymon.
Solutions
Solutions were posted in monthly postings, as well as compilations at the end of each year. Here we list the year-end solution files, as well as the monthly files from January 2008 to June 2010.
2000: Problems 1-54
2001: Problems 55-126