The only altcoin I have any faith in at this time are Litecoins. Litecoins ARE a necessary diversification away from BTC should something bad happen to SHA256 and whatnot
![Grin](https://bitcointalk.org/Smileys/default/grin.gif)
I think everyone here would agree with me in that it's never wise to put all of your eggs in one (BTC) basket.
![Smiley](https://bitcointalk.org/Smileys/default/smiley.gif)
What's SHA256?
It's the encryption algorithm that is used to mine bitcoins. Litecoins on the other hand use scrypt algorithm during mining.
For a super sciencey answer try:
https://en.wikipedia.org/wiki/SHA-2