Once the first lemming is walking towards the first pillar, make him
a climber and a floater (athlete). Climb over the first column and
proceed to the second. Climb over the second. Before reaching the
third build so the lemming turns around. Use 1 or 2 builders to reach
the second column, so the falling distance is safe for lemmings without
umbrellas. Repeat this procedure for all the other columns. Dig throuh
the slope and bash to the exit. Make all the other lemmings climber when
they are walking towards the first pillar. (This is important, if they're
not walking towards the first pillar and are made climbers they'll climb
off the level. Result: 24 dead lemmings)
Blitz 2: Lemmings Up High
There is a bump on the platform the Lemmings fall onto that is lower than the other bumps. As soon as Lemming 1 walks past that bump, make him build. Make Lemming 2 dig in the bump so it's deep enough to hold the Lemmings. When it's deep enough, build. Lemming 1 builds up to the exit. Use builders to build out of the now deeper bump.
Blitz 3: Check Your Hints!
Bump the release rate up to 99. Let the lemmings walk till they're above the 7th exit from the right. Make Lemming 1 dig at a deep bump.
Blitz 4-16: Unavailable
The title says it all. If you have written a walkthrough for any of these levels, feel free to submit it to me.