TeXShop: Latex rulz. At least, whenever it's not driving you mad. If you don't work on a Mac, WinEdt may work for you.
Open Office: for compatibility with the rest of the world, and this one is free!
Adobe Indesign: this is just the thing for page layout design, but it is not cheap. You can try instead Scribus, which is totally free, multiplatform and has the most important features. Both generate PDF documents suitable for on-line publishing in, e.g. Issu.
I'm kind of partial myself to Adobe Photoshop, but it you need something good and free, go for Gimp.
To switch video formats, I usually dig MPEG StreamClip in my Mac, but I was very fond of Virtualdub on PC. Take your pick.
If you are working on PC and need to play mov videos, I'd go for Quicktime Alternative. It works faster than Quicktime and mess less with the system.
I'm sorry to say it, but I don't like iTunes just one bit. Too many limitations, too heavy for the computer and one has to be extra-careful with unwanted synchronizations. I've always been fond of Winamp, but the Mac version still needs some adjustments.
And, if you want to move things from and towards your iPod, you can always use (free) De-tune (for Mac only)
Grooveshark: Cloud music player, free (until now)
Dropbox: to keep your files synch-ed in all your computers
Dropbox Encore: to overcome the limination of one accound/one Dropbox folder (for Mac only)
Evernote: to share notes between Android mobile phones and computers
Settle Up: to quickly fix expenses when you go out with a group of people