We have got good response through kijiji. There is definitely a lot of renters that turn to kijiji...and it's free to post and search.
Kijiji is also a good spot to get rent comparisons.
Rentspot is another free search site, but will cost about $7/month to post.
If you have a property near a secondary school and are targeting students you might want to contact the school (SIAST, UofS etc.) to see if they have a public board/web to post such listings. Same goes for hospitals - ie, nurses.
If you are doing an executive rental, getting in contact with some of the bigger company's (BHP, AMEC, PCS, etc) HR department might land you something.
My wife and I currently live and invest in Saskatoon. We'd be interested in touching base with you to share any info that might help one another out.
Good Luck!!
Brady