My layouts always come out too square...
Any good tools/tips to solve it?

use rounded imgs for a border.

It sounds like cop out advice, but if you think your designs come out too square look for ways to get curves in them.

Rounded corners on images, try a few effects that give subtle 3d appearance. Look for tutorials for whatever image editing program you use and learn some ways to create a small effect here and there.

You don't need a lot of curves. A few here in the right place should be enough. Too much and the designs won't look right either.

Also anytime you come across a site with a design you like bookmark it and study it. Try to really understand what it is that makes you like the design. It might be the color scheme, it might be one or two details. Once you start to see what you really like try your best to learn how to do the same.

Take a look around this site: http://www.csszengarden.com - lots of NON-SQUARE ideas

Something you might try is, if you're using a defined container, bleeding some things slightly out of them. Cluster smaller sections with larger ones, and shift them however it is necessary to avoid the look of rows of boxes. Think about where you want the eye to go when the viewer first looks at your page. Non-rectangular sections, if well-done, can also help. Rounded corners have been done to death, IMHO, but I suppose can still be used sparingly.

tim