This is confusing, EP I thought you were asking about a hard copy portfoilio is this correct.
A web portfolio is a different story.
A hard copy portfolio should contain a minimal but vastly varied amount of work, you don't want to overload the person with everything you own but there has to be a wide range of materials.
Find out as much as you can about the company, most design houses dable in eveything but specialise in one thing inparticular. This is how they maintain a place in todays market. Find out what they specialise in then you have a bit of inside information.
It doesn't hurt to have pages of written information about the company in a see through folder for the employer to spot. This looks like you've researched the position very well and you are interested in the company as a whole. An employer of mine once said...
"You can't be over pushy, push and push some more, go as far as you can, you know you've gone far enough when you're contemplating getting the companies logo tattooed on your a**e"
Another thing to remember is in this day and age people aren't only looking for a great designer, they want someone that knows:
• Sales Techniques
• Print Production Methods
• Market Research Awarness
• SEO (if web based)
• Spot colour and process experience
• Integrated Products
• Security Products
• Web Standards (if web based)
etc.
You get the idea.
Good Luck