If you live anywhere near a sawmill, you
should take advantage of the fact that most of them will let you haul away as much sawdust as you can carry. We have one less than a mile away and that has been our mulch of choice for years. We tried straw a few times, but the introduced weeds in an area formerly prisitne (no weeds -- just
native plants) was too much for us. We spent more time trying to put a check on the
dandelions and plantain sprouting through the woods and glades than we would have weeding the garden!
Be aware that sawdust is not only acidic, but because it takes a couple of years to break down completely, it robs the soil of nitrogen as it decomposes. Using it with a generous amount of farmyard manure (well aged -- never straight out of the coop or barn!) makes a great combination. It looks pretty and neat too -- unlike newspapers.
One other thing... Sawdust will lift and float away when you get a heavy rain or water with a hose. To get around that, you may need to use some edging material (especially if you are on any kind of slope). For ordinary watering of plants, we dig a small hole next to each plant as we set it in the soil in spring (not for row or field crops but for things like tomatoes, peppers and squash) and then set a steel can with a hole punched in the bottom about 1/3 of the way down in the hole. The sawdust gets piled around that. When we water, it only takes a minute to fill each can and let it slowly trickle into the soil around the
roots of the plant. No disturbing the sawdust or wasting water by letting it evaporate from the soil surface.