I just downloaded the Ethereum Wallet for Debian Linux (I have Ubuntu 16.04). It appears to be downloading a lot of blocks: it now says that there are 3,310,606 blocks, and the number is decreasing. I also see a new .ethereum folder in my home folder, which is now over 602 MB in size and increasing.
I am almost out of memory on my laptop. Is there a way to use Ethereum (including some simple smart contracts) without using so much memory?