You can use your losses from stock market transactions to offset the gain on the sale of your house (provided you are not in the business of flipping houses).
This may not help much if the actual tax on the gain from the sale of your house is $500,000, but you can take advantage of the Section 121 exclusion if you owned and used the house as your primary home for the last two out of five years leading up to the sale.
See https://www.irs.gov/taxtopics/tc701
