Hello. I would like to get a recommendation from you, which module should i use in my XOOPS site. I'm planning to make a little "shop" here for selling software. There will be a little description and general info about every product, price and link to buy product. all ideas are highly welcome.

Simple Paypal buttons are one way to go for a small shop. I personally would go for cubecart http://cubecart.com/ or zencart http://zencart.com/ as standalones with links from Xoops.

Another solution would be to use mals free e-commerce as a hosted cart, and use it from a content module. http://www.mals-e.com/ Mal's service is used by many thousands, gives more choices regarding payment gateways than paypal alone.

If you want a bigger shop oscommerce is the most well known, there is a module somewhere if you do a search, I don't think it is currently being updated, not sure, but again, if using this solution I would personally go for the standalone version.

Yeah, these systems are not bad, but don't need all these features yet. Think to install FreeContent, Tiny Content or something like this and create simple html page with products and links.