I know HTML and CSS. From XML, JavaScript,...

[writer68]

...JSP or CGI, which language would be quickest to learn next? I'm trying to learn a new "web" skill for a position in my company. I was told I should pick up the skills I outlined in my question, but I am unsure where to start. Assuming each language/skill is equally important, which would be the best to start learning. I know there are other web skills to learn (PHP, Ruby to name a few), but I was only asked about the above skills.

If there are any recommended books, web sites, etc anyone could provide, it would be helpful as well.

[alan s]

Start with HTML it's the basic building blocks for web.
There are loads of good tutorials on this site
www.w3schools.com
They cover HTML, XML, ASP etc etc, all very good.
To learn, copy and paste their examples into notepad (or similar text editor) and keep on your own pc. This enables you to refer back and try your own things even when not online.
Some technologies, like ASP, you will need to do online unless you have an IIS setup. But you can find free hosting sites where you can trial your own web pages etc.