Candy bar

CandyBar allows you to customize your icons with ease and to download premade sets making the job really easy.
The problem is that you have to pay BUT their is a trial, so you can change your icons with no problem and then you can or stick with them and i think you can revert back even after you trial ends (needs confirmation, post a comment if this is true false please)
http://www.panic.com/candybar/

Open office

With the new office starting at 150$ (education price) and getting a rating of 2.5/5 on the apple website, a free, non glitchy alternative sounds good
Open office is a great replacement for microsoft office, and it can save in .doc (microsoft word's file type) so it is fully compatible with microsoft office!
I see no reason not to switch to open office

http://www.openoffice.org/

gimp

gimp is a powerful photo editing software, and is free!
it is a great replacement for photoshop.
Installation is a tad more complicated, but the process is clearly indicated:
http://www.gimp.org/downloads/

Corripio

With cover flow integrated into finder and into every ipod besides the shuffle, album artwork is something one wants to have.
To save you the hassle of searching for each one individually, Corripio does this automatically.
If the information (album, artist, name) of the song is complete it will find artwork easily, it also works when you only have the name and the artist, but usually brings out a selection for you to select the correct artwork
The find lyrics feature is not very good, i recommend using pear lyrics (2 posts down) to find your lyrics
http://nclasssoftware.com/corripio

autorate

A program that rates your songs based on play and skip counts. From personal experience, it rates songs quite accurately and works fast.

http://tzisoftware.com/products/autorate
(download on bottom right)

Pear lyrics

Pear lyrics is a program designed to find song lyrics for your songs in itunes.
It works great and finds lyrics fast, it found over 50% of my library (and i have alot of bands that are unkown to many)
Its small, but had some legal issues, you can still grab it with the link below:

http://www.macparc.ch/mirror/pearLyrics/

netvibes

not a program, but a website made for you to have a personal homepage. You can add rss feeds, your mail inbox from many different services, games, comics, weather and such.
It is completly free, check it out at:
www.netvibes.com (add our feed!)