When you buy land or an interest in land in Ontario, you pay land transfer tax. First-time homebuyers of an eligible home may be eligible for a refund of all or part of the tax.
For more information view CRA's website at: http://www.fin.gov.on.ca/en/bulletins/ltt/1_2008.html
The sale of the severed portion of vacant land would not be subject to GST/HST since it is not capital property used primarily (more than 50%) in a business and it is not being sold in the course of a business. However, if the land was subdivided into more than two parts, sales of the severed portions are not exempt unless the portion is sold to a relative (or to a former spouse or common-law partner) for their personal use.