Small but useful points in Adams v Association of Professional Engineers (Ontario), 2012 ONSC 3850, and Kandolo v Kabelu, 2012 ONSC 4420.
The OBCA, the CBCA and the new Ontario Not-for-profit Corporations Act 2010 provide that a director's resignation is effective on the later of receipt of the resignation by the corporation or a date specified in the resignation, does not need to be accepted by the corporation and cannot be revoked once given, unless the corporation agrees. The position is less clear for corporations with share capital that are governed by the Ontario Corporations Act (and the common law), but the 'prevailing view' (according to the Adams case) is that a resignation is effective once given (not received) but also does not have to be accepted by the corporation; revocation is likewise possible only with the consent of the corporation. The court in Adams didn't think that different principles should apply to Corporations Act not-for-profits without share capital, unless the by-laws specify anything different. The whole point of the rules is to allow a resigning director to know when his or her liability will cease and to give the corporation certainty as to the composition of its board.
http://www.canlii.org/en/on/onscdc/doc/2012/2012onsc3850/2012onsc3850.html
http://www.canlii.org/en/on/onsc/doc/2012/2012onsc4420/2012onsc4420.html