Native pollinators are as important (if not more important) than honey bees for pollinating crops and native plants. There are a few things you can do to attract native pollinators to your garden:
Grow flowers and let your veges flower to feed the pollinators all year
Have a source of insect-friendly water in the garden (shallow dishes are best)
Provide somewhere for them to live/nest/lay eggs - a bee hotel!
In Australia, our native pollinators consist of both stingless native bees, which live in a colony like honey bees, and lots of solitary bees and wasps. These solitary insects are just looking for a suitable hole to lay their eggs. You may be familiar with these in sub-tropical and tropical areas, in summer you will find any and all holes, pipes and tubes around the house plugged with mud by what we call "mud daubers". These area a real nuisance, so I'd rather provide some custom holes near the garden where they can live instead, so I don't feel bad about removing the ones around the house. As well as pollinating flowers, some also predate caterpillars and other pests.
Some people make really beautiful bee hotels, but we like to keep things cheap, quick and practical here. Plus this basic model took me over a year to complete, so lucky I didn't try anything complicated. We started with a log with a hole in it and Pete drilled different sized holes all around the outside. Then I "found" some dead bamboo growing around Spring Hill when I was working in Brisbane and brought it home to cut to size until we had enough to fill the centre of the log. Pete then mounted the log on a piece of metal (this part is only necessary if you have a metal trade, anyone else would use wood) and we put it on a star-picket next to the garden.
Its been up for a few months and we already have some tenants. I'm looking forward to seeing what ends up living in the bamboo. If you've been thinking of making a bee hotel, this is a very simple way to add some native pollinator habitat to the garden.