Retrieving stock prices
Now, I don't know much about webscraping, but I don't think there's much you can do to make this method of going about it any faster. You're restricted by how fast Internet Explorer can retrieve the website. There's also the fact that VBA is a single threaded language. So, multi-threading is out of the question.... or is it?

I would tackle this problem a little differently. I would create a swarm of VBScript scripts to retrieve the data you're after. This works by using VBA to writing many VBScript files to a drive location and using a shell to execute them. Each VBScript is responsible for writing the data it finds to the appropriate cell in Excel.

You can find a reasonable example of this (including a workbook with the code) here courtesy of Daniel Ferry.