Just search it on Google Images with the usage rights setting on 'labeled for reuse with modification'. Simples.
Personally, I like mayang.com's textures
Uhhm. I guees you didn't really understand what I was looking for. Again: I am not looking for pure or so called "plain" textures of specific forms like straw or hay. My Problem is to find a "technique" to create overlapping straw, which goes over the titled edge of the texture, to be used with an alphachannel.