Check out:
https://www.cryptsy.com/As for easier to mine, the comparison isn't exactly logical.
Proto is CPU mined while doggy is GPU on scrypt.
With lw hashing you can get plenty of DOGE, but the exchange isn't that great.
While PTS is exchanging at high value, but very difficult to get a good quantity without investing in some good computing power.
That being said check this post out to get started with proto mining, it will give you an idea of what to expect:
https://bitcointalk.org/index.php?topic=347212.0