Capital losses can be used to offset capital gains. If there are excess losses, they can be used to offset up to $3,000 of ordinary income ($1,500 for married persons filing separately), which includes interest on bonds that are not tax-exempt. Any excess loss can be carried forward indefinitely and used in the same manner.
Increase in value of property due to market conditions. When you sell appreciated property, you pay tax on the appreciation since the date of purchase. When you donate appreciated property held long term, you may generally deduct the appreciated value.