Here is my 2nd block I am doing a litte better getting the blocks to line up.It is harder than I thought it would be.

I love those colors they are my favorite.
very nice block too.

Oh my that is pretty. I love blue and your square is so pretty. Great job.

I've made several of these blocks and had the same problem with keeping it square; think it has something to do with the fact that you are taking a 1/4" seam on the half triangle square and butting up to the full square.

Wow - this is going to be a very pretty quilt once you get all the blocks joined. Nice job!

Here are some tips that might help you.

The more accurate you can be on your HSTs the easier it is to sew them together.
On the first block - on the rt side if you sew along the last 2" of the middle seam to that outside edge you can tighten that seam and pull that edge into a straigher line. Sew over from the seam about an 1/16" or a 1/8" depending on how much it takes to make it straight.
On the left side I would pick out the last 2" of that middle seam and tack or pin the corners of those two blocks together. Then sew them back together and you should have a straigher side. then trim the block square leaving your 1/4" seam allowance.

My easy to make HSTs and tips
http://www.quiltingboard.com/t-37915-1.htm
http://www.quiltingboard.com/t-23252-1.htm

Wow! What an improvement!

I have all that fabric, too. What excellent taste we all have!

Oh you are making progress, this is looking much better, and very pretty. Congratulations, you are a quick learner!!

I love blues! It should turn out great!