There are many reasons to love Thermal Expansion, but I only recently found out about the (literally) cool things you can do with its anti-lava, Gelid Cryotheum. First off, allow me to recap how to obtain it.
TE adds a new mob that is an icy counterpart to the Blaze - the Blizz. Blazes drop Blaze Rods, so Blizzes drop... surprisingly, Blizz rods. They spawn rarely in icy biomes, i.e. in Taigas or the fabled ice plains, which I never saw so far. Rare means rare, so unless you really like playing the hard way, a Peaceful Table will eventually earn you some rods if placed in a Taiga biome.
Pulverize the rods to get... Blizz Powder.
1b. No Blizzes!
If that all sounds tedious to you, just get yourself some snowballs. Easy, right? If not, find yourself someplace snowy and whip out a shovel. Note that they only stack 16 balls high.
Now place the snowballs in a Fluid Transposer, melt Redstone in a connected Magma Crucible for Destabilized Redstone, and be amazed. TE apparently included this recipe to allow for late-game mass production, but it will save you the need to hunt for Blizzes altogether.
2. Mix It
Apart from the powder, you need (more) Redstone dust, (more) snowballs and Niter. The latter can be obtained as a byproduct of pulverizing Sandstone blocks. You will get enough sand back to reconstruct half of the Sandstone, and one stack will usually yield 8-10 Niter.
If you got it all, just place the stuff in any 2x2 crafting grid. Profit!
3. Melt It
Gelid Cryotheum is a dust that does not do much, so you first need to melt it in a Magma Crucible (yields 250mB, so 4 dusts to a bucket).
4. But What Is It For?
If placed on the ground, Gelid Cryotheum acts much like a turquoise variant of lava, and will hurt you just the same. It will obviously not set you on fire, but that frostburn hurts, so be careful. It will destroy grass blocks around it just like lava, but it will (of course) not set fire to anything. In the open (not tested indoors yet), it will also spontaneously generate a snow cover on surrounding blocks. Which is a nice way to get more snowballs in a hurry, although a TE Glacial Precipitator is a lot better at generating them.
4a. Make Traps!
Cryotheum is a nice filling for drop-to-your-death traps, as it will kill anything unlucky enough to fall in, and has the added bonus of not setting fire to its surroundings. Build a nice wood-framed trap and snigger if somebody falls into it because they thought that there could be no lava here, or it would have burned... waaaaa!
4b. Cool Things
As of the latest patch, Big Reactors finally acknowledge that the icy stuff is indeed a hyper coolant. I think it surpasses Resonant Ender now, although test results are still pending. It also looks damn cool (pun intended) inside that reactor casing.
A very slow-flowing icy waterfall may be just the thing to top off your Taiga fortress. Or how about a moat of icy death around your compound?
Feel free to add anything else that can be done with it, or point out if I got something horribly wrong. I am picking this up on the fly, and sometimes I tend to be stupid. Credit goes to KingLemming and the awesome TE crew, and all the helpful people from whom I picked up all those information snippets.