I haven't resorted to gravel yet but I did add some perlite to an area to grow carrots last season. It'll be nice to see what it looks like this spring.
If mulch is hard to come by and you're not bothered by not having the wood-mulched look, you could try the chop and drop method. I'm really having to focus on that when I'm pruning during the growing season. I think Hazelnut posted some neat links in another thread.
