I've crafted the below guide and provided text descriptions below it. For most of these you can simply turn around and try again if you miss. Tropico is by far the hardest.
Downtown Rush -
0:04 - After the huge drop near the end into the flooded city, the course will turn right. Instead of turning, go straight off a ramp right into the middle of a hole in the building. The egg is inside.
Fountain Park -
0:18 - At the end you'll crash through a glass wall after moving through a harbor. Move to the left and crash through the statute just behind the window. The egg will be in a glass box just behind the statue (on the left).
Unicorn Base -
0:32 - In the first area with the battling ships, go directly left and boost off the red ship there at full speed. The egg is in the air.
Sky Mines -
0:43 - At the end it's in the middle of the vortex with the laser coming out of it just before the finish line.
Grindhouse -
0:52 - Just after starting lap 3 you'll come to the area where you can now go straight through the middle. After jumping to the higher platform, turn sharply 90 degrees to come to a stop, then slowly move forward and fall off the edge in the middle of the path to hit the egg in the air.
Tropico -
1:11 - This is very hard. You'll need to watch the video. You need to play against Pro AI so that you can drift behind them to get the speed boost without passing them. The cops will be annoying. In the half pipe, you'll turn left once and then boost into the next wall angled slightly to the left. The egg is high up in the air. Watch the video to see the proper line (it's impossible to describe).
The Ruins -
1:33 - After you get through the storm you'll move through the city and pass a ramp. After the ramp keep heading forward and behind a rock you'll see a hole in the building (the course will move to the right). Go through the hole and you'll see the egg next to a waterfall on the other side.
Alpha Station -
1:50 - After jumping into the area with the forked path (right before the giant turbine that pushes you up), hug the middle and go around. You'll see the egg just behind the big platform which you're hugging.
Firewater -
1:59 - Boost off the second big jump, do a trick to maintain some boost (but not a long one - do a double back flip), then veer to the left. You'll see a ramp. As soon as you hit the ramp do a triple front flip to push yourself up and get the extra height you need to hit the egg.