In case you're considering making your own nest box for critters, I thought I'd include some examples from my clever friends and some more links for additional information.
Not only are bug/bee/insect homes an easy project (I made ours!) and a great way to encourage biodiversity in your garden, but they can be ornamental as well.
Below is a stunning one Lea Casey made. Lea told me before she started that she thought it may even be "a 5 star tower block complete with gym, bar and swimming pool"; and I think it's all that! Something I'm yet to do is create some sections filled with soft mortar, so as to offer homes for the insects who like to dig holes for their nests, like blue banded bees.
Another artistic friend, Joanne Diver, entered a "Bee Inn" in the Rutherglen sculpture trail this year, and was awarded an honorable mention.
Joanne has also made some other smaller ones for backyards which she's selling at the Albury Twilight Markets, so if you want one ready-made, get along to grab one of those!
Alternatively, if you're keen to make your own, there's plenty of information for reference. Radio National featured a grand 'bee motel' and interesting interview, featuring Honeycomb Valley Farm, Nabiac, which you can listen to here. The people who created this bee motel have a native bee sanctuary (among other interesting sustainable living features and farm stay). And there are a whole load of fantastic fact sheets by Valley bees, which you can view and download here. Instructions for creating bee habitat and homes are among them.
Some of the gardening and lifestyle shows/magazines have also had good insect and native bee habitat items, including Gardening Australia, Organic Gardener, Better Homes and Gardens and Grass Roots. Millie Ross has been an advocate for some time; here is an article from 2010, while her recently released book, The Thrifty Gardener, also contains a how-to.