I think I jump in.
The most important tool for me, as a so-called web designer, is the code editor. There're plenty of options out there, but my personal choice would be Panic's Coda, but recently I've been playing with Sublime Text and found to be a superior code editor of it kind. I'm jumping from Mac to PC from time to time, so having Sublime Text running on both system has been really helpful for me, but I just could not abandon Coda because of some of its own great piece of software with a lot of functionality.
Also, I have a whole set of Adobe Creative Suite Design Premium but I don't use all the software. I usually use photoshop for most of my graphic/image editing, illustrator for logo design. I also use an image editing software called pixelmator in my Mac and I think it's great. Check it out at pixelmator.com.
If your brother is serious about expanding his skills to the web, give him a subscription to tutsplus.com . This site helps me a lot in honing my design skills.