Is there a mining software that I can run on my webspace (php, ruby, python)? Is there a miner written to be run on webspace, e.g. in ruby, php or python?

I know, it will be to slow and its not worth it, but I want to see it though :)
You should look into webminers - What is the status on webminers?

But generally, it's not really worth it. Unless you get a lot of high-end-graphic-card-owning users to stay on your website for a long while, you won't earn much. You can try running some of the webminers on your own machine and see how much you can earn for example by using my Mining Calculator. Having someone with a 100MHash/s graphic card (fairly decent for a non-dedicated miner) on for 24 hours would give you about a cent of revenue.

All in all, you're probably better off with adding some ads to your website.