For a recent project I was quoting I was looking at a product called Lindapter. You can see their site here. They have some cool products that can be used for attaching structural steel pieces to other pieces without damaging the steel. It also means that there is no welding, and that they can be removable. The downside is that they are fairly expensive (50 or more each), and can have a long lead time.
I would think that this would be worth though for critical applications, and would be useful for installing grids.
They also have a product called a hallo-bolt that is used for structural steel. As you tighten the bolt a nut inside the steel expands trapping the bolt securely. While I can see definite uses for this, it is out of the price range for most situations considering the pricing starts at over 10 dollars for a single bolt.
Nevertheless, the types of products they sell gave me some ideas about how I could make some nonstructural connections easily.