(Most of these have version/variations for PC, except they're less cool) I will continue to update this post as I discover new tools, or based on submissions from all of you.

Skitch - Screen grabs are critical for putting together presentations and saving important activity on the web for your archives. While Macs have a solid built-in screen grab tool, Skitch takes the process further and gives you more flexibility with sizes, lets you add notes, and creates a visually pleasing history of all your screen grabs. Most importanty, it automatically saves them on your computer AND online if you prefer. Skitch Website. (I also use Skitch when I'm working with my Bamboo pad).

Adium - iChat is a great tool, but there are far more instant messaging clients out there that people use across the world not supported in iChat. Adium is an excellent tool for taking up to 18 different programs and cleanly laying them out within one window. In PR you need fast access to a variety of individuals and you don't want to be fumbling around with different programs or web interfaces to get in touch with someone. Adium Website

Garage Band - Amazingly, this was actually a recent discovery for me. While you might think a program like this is meant only for musicians, the digital PR professional can absolutely make use of this program for their work. Garage Band has one of simplest podcast recording tools yet gives you all the tools you need for a quality track. For files you receive that you need to edit, it allows you to easily reconfigure tracks as well as add background effects/music. Garage Band Website

Snackr - Snackr is a RSS reader like any other, but rather than having a window open with a list of your news, it scrolls them randomly across the bottom of your screen much like a stock ticker. You can set the tool to show you news from the last 1 to 30 days and when you click on one of the titles, a window expands within the program showing you the full text. I recommend Snackr because it is a more passive experience that still allows you to stay up to date with the news by glancing over once in a while. Snackr Website

Skype - A well known tool, but often forgotten by many folks in PR. Especially for those who work with international clients and team members, Skype is a cheap and fast way to talk to people around the world including the ability to conference up to 25 people. Skype simplifies the process of worldwide calling because you don't have to worry about conference numbers or memorizing people's phone numbers. Additionally being able to have a chatroom with others is a handy feature for sharing links while talking through business. Skype Website

Parallels - So you're one of the few digital PR people who decided to switch to Mac? (Most have not) Then you might want to consider installing Parallels on your computer. Sadly, there are still programs out there that only were built for PCs and for those working on tech clients, there are going to be times that you need to be able to test out those programs. Paralles is a simple tool, that creates a temporary "PC" on your Mac so you can still run that type of software. Parallels Website (Buy it on Amazon)

Socialite - A Mac application that acts as an all-in-one social aggregator. If you're monitoring a client's brand on a daily basis and aren't looking for the macro reporting that a Radian6 or Techrigy offers (and charges for) then socialite is a nice solution. One handy feature is the "quick send" option that essentially runs the program in the background but keeps a small window on your desktop that lets you update your status on Facebook, Twitter, etc. This is a useful feature when you need more space on your desktop for other work. Socialite Website