Interesting topic
I'm always on the lookout for storage ideas and solutions myself. I've only got a handful of rotary mowers which haven't caused me any storage issues so far. However my wife would like my collection of cylinder mowers to take up less space but I don't think racks will be easy with something of that weight and size.
I have a reasonable stash of car parts and like Blue, I use the plastic tubs and lots of shelving to store most. For those that don't need to be kept dust free, I use a lot of old milk crates and bread trays as they also stack very well and are quite sturdy. I grab them from the tip for $2ea.
