Although they used to say no stenuous exercise for 24 hours after donating a pint of blood, now they are saying 48 hours.
To be honest, losing a pint of blood will make you very suseptable to dehydrationg and passing out with heavy or sustained exercise and the donation site may start bleeding again with the increase in blood pressure from exercising.
I DO go to the gym the morning after giving blood, but I cannot do my regular routine and definately have to take it easier.
I would not recommend running/jogging at all the same day that you give blood (just from my personal experience).
from the American Red cross Website:
How can I ensure a pleasant donation experience?
You'll want a good night's sleep the night before, and a good breakfast or lunch before your donation. Drink fluids like juice, milk, or soda ahead of time. Take your normal medications as prescribed. Ensure you have adequate iron level by making iron-rich foods part of your daily diet. These include red meat, poultry, fish, green leafy vegetables, iron-fortified cereals, nuts, raisins and prunes. During your donation, relax. After your donation, have some juice and cookies in the canteen. Then you can go about your daily activities, but avoid heavy lifting or strenuous exercise for the remainder of the day.