OS X may not have the same applications as Windows, but there are plenty of options out there. Some of them are free, but others cost money. It usually isn't much, and they're often worth the investment. I'll be covering the text editors for my first installment.
My personal first choice for text editing is is the aptly names TextEdit. This simple text editor may not look like much when you first open it, but it can easily be converted into a usable editor for writing up papers. It has more features under the surface than you first realize.
When you first open text edit, you'll get a little window that shows no margins, and very few toolbars. Go into the preferences (TextEdit --> Preferences), and set these options:
After these options have been set, you should be ready to go. I use this text editor more than any other for writing, but when it comes to Programming and Web Design, I have other favorites.
This text editor specializes is HTML and PHP. I found it a couple years ago, and I have yet to find anything better for either HTML or PHP. Projects and Live Preview make things easy when I'm getting well into a web design project, and clips save time during repetitive or unwieldily typing (for instance, you have a header you want to use on ever one of your pages that's 12 lines of HTML, so you save it as "Web Page header" clips, and by pressing a hotkey, it'll insert your clip into the document).
One "hidden" feature is opening a document template by default. Just make that template, and save it somewhere where you won't move it. Go to the Preferences and click on the documents tab. Click the checkbox labeled "Create new documents with the code from the following file," and choose you file.
SubEthaEdit is my personal choice in text editors when it comes to programming anything other than HTML or PHP. Its collaborative text editing is the best I've seen, and is great if you use it in an instructional environment or are working on a project with someone else. I don't have any tips or hidden features on this one.
Part of iWork, Pages is a layout and text editor used for making "pretty" things with text. I use it for making invoices and school stuff that requires more advanced text editing. Think MS Word without all the needless annoyances and a very nice template system. Easy to use, and it has a very low learning curve.
I don't use these much, if at all, but they're worth consideration
The next software topic will be Web Browsers.