Is there a place where the Difficulty Values are tracked and archived?

For instance, at present the difficulty value is at: 1755425.32

Everyone says, this is quite high and it wasn't this much 3-4 months ago. Alright, then what was the value back then? Where can I find more details?

Let's say, what was the average difficulty value in the month of March?
The value of 1 BTC against 1 USD in March?

It would be interesting to see how it has changed over the past few months and we can even project how we expect these values to change in the coming months.

As the word spreads around, more and more users are going to join the Bitcoin Network. Existing users are going to rack more GPUs in parallel to have much more powerful mining rigs.

So, the difficulty is going to increase with time, which means the possibility to make BTC will keep decreasing.

It's becoming a game of endurance.

I just came across Bitcoin and I am new to it.

I have registered on Deepbit.net Pool and I am using GUIMiner software running on Windows 7.

I logged in using my Deepbit credentials. However, I am confused about the Bitcoin address?

On Deepbit.net under statistics, it asks for my bitcoin address. Where do I get that?

Do I need that address to get bitcoins? Currently, I don't have the bitcoin client installed on my machine. Only GUIMiner and I am directly connecting to the Deepbit.net pool.

I am getting an average speed of 80M Hashes/sec which I suppose is ok? Reward Estimation says, I'll earn 0.04 BTC in 24 hours. That's very less.