Mac running slow – do I need more memory?
If you are running OS X 10.3 or 10.4, try running Activity Monitor, located in your Utilities folder (don't know where that is? See next tip). This will tell you if you are using up all of your available memory. If it isn't check if your Mac is running a lot of processors you have absolutely no idea about. Could be a rogue printer driver or an old version of software that needs updating.
MenuMeters is an excellent alternative that shows you what's going on all the time in the menu bar.

Upgrading to OS X, all confused? Get a book!
Check out the titles under The Missing Manual series. This one is for OS X 10.4 Tiger.

How do I backup my iPod (and other naughty questions)
Well, we're not going to tell you how, but
this mob has many useful tutorials.

I'd like to transfer my DVD movies to my iPod. What do I do?
That's actually two questions: how to extract movies from a DVD, and how to move it to an iPod.
For the first half, check out the Mac forum
here. For the second half, the official answer is to use Apple's QuickTime Pro. The other answer is to visit the mob that has a lot of useful tutorials on the iPod above, or use one of many excellent tools available, eg iSquint on the Mac.

I'd like to find some software. Is there a simple way to search on name or function?
Apart from Google, try
VersionTracker first.

How can I find out more about my Mac, like speed of memory, model year?
MacTracker is definitely one of the best resources around.