If you want to be more of a client side programmer, the following is a good list.
JavaScript -- For client side interaction. Look up the term AJAX, which incorporates JavaScript, and you'll see all sorts of people talking about how this is the future of web applications. Gmail is an example of an AJAX application.
CSS -- Not a scripting language, but a way to style and layout web pages. Alot of people use CSS wrong. There are a few books that cover how to do it right. Books by Eric Meyer (Eric Meyer on CSS 1 & 2) and Jeffery Zeldman (Web standards) are MUST READS if you want to learn it right in the shortest amount of time. You might work witha designer that will do all of this for you, but you still better understand it.
HTML -- I'm sure you know this by know, but the trick is doing HTML right. The Zeldman book talks about this and the O'Reilly HTML reference book is very helpful. Don't fall into using HTML the wrong way since it is very hard to get out of that pit. When I say "wrong way", I mean using tables to layout your page instead of CSS or .
XML -- Not really a scripting language, but you'll need to know how to use XML in relation to other scripting languages.
XSL -- I have read a little about this, but don't really know how many companies are using it in the real world. There is a slight bit of scripting involved. Read up on it just to be aware. I still believe most people are sticking with HTML and CSS.
For backend programming, which I don't no much about,:
ASP or ASP.net -- If you end up working at a company using microsoft products, you'll need to know this. They are very similiar to PHP.
SQL -- Not a scripting language, but you'll need to interface with databases and this is the only way. SQL syntax varies by the product you use. MYSQL, SQLServer, Oracle are all popular database products.
VB or VB.net -- If you are in a microsoft shop, they'll want you to know this.
C# and/or Java
C++ -- If you want to get hard core.
There is definitely more stuff out there. I recommend looking at some job descriptions of jobs you might want and check out their requirements. That's the best way.