Don't use wood chippings! Apart from the fact that they take aaagggggeees to rot down (4-6 years), and as they do so they reduce the nitrogen levels in the soil and inhibit seed germination. Don't know the science behind it, just remember reading it in lots of places when we were deciding what to bed our hens on.
If you can get hold of it the best thing is grass that's been through the stomachs of a cow or a horse - there's not much better for upping the level of humus in your soil than manure, preferably well-rotted. If you're sowing seeds direct it needs to be worked in to the soil otherwise it will smother them, but if you're planting out seedlings leave it on top as a mulch - it's not too late at this time of year and the worms will drag it down through the topsoil as the season progresses.