Geeky/Utility

AppFresh

Keep your Applications up to date. Also ties in with i use this, so you can see what people like you are using on their Macs.

Growl

Highly configurable notification system. Tons of apps plug into Growl to give you a nice consistent way of being told about stuff. Can even send notifications to your iPhone.

Transmit

FTP client with a nice interface and lots of features, including support for Amazon S3.

Disk Inventory X

Disk usage viewer. Similar to KDE’s KDirStat.

VirtualBox

Sun’s free virtualisation software. Run Windows or Linux in a virtual machine on your OS X desktop.

Chicken of the VNC

Friendly VNC client.

Super Duper

Disk cloner.

Mac Pilot

OS X preferences adjuster. Fiddle with OS X settings in (relative) safety.

SoundSource

Menubar utility to change your sound input and output devices without diving for the System Preferences.

MenuMeters

Put CPU, disk, network and other meters right in your menubar.

Hazel

Keep your Mac tidy and organised, without doing it all yourself. Hazel will organise your desktop, file downloads into the right places, even zip things up and set their Spotlight info.

Audio

Airfoil

If you have an Airport Express with iTunes, or more than one Mac, try Airfoil. Send any audio to your remote speakers, use another Mac, Apple TV or even an iPhone as a remote speaker, play video with the soundtrack synced perfectly on your remote speakers.

Weird and Wonderful

Pzizz

Helps you get to sleep, or take power naps (really!) Odd, but definitely worth trying if you feel a little run-down during the day or have problems getting off to sleep at night.

Games

Oolite

Open source Elite clone, with spookily identical playability to the original.

Graphics

Freeverse Lineform

Vector drawing package that I use to draw things like this. Unfortunately not so compatible with Snow Leopard, and currently a but buggy and under-loved by its creators.

Pixelmator

For normal, non-vector graphics, if you can’t afford Photoshop (and let’s face it, who can?) Pixelmator is beautiful, functional and affordable.

Photography

FlickrExport

Export directly from iPhoto to Flickr.

Web Design

RapidWeaver

Theme-based web development. If you want a good-looking, full-featured website in a hurry, and you don’t want to break the bank, go get it.

RapidFlickr

RapidWeaver plugin that creates a gallery based on Flickr photos.

Coda

If you hand-craft your websites, you can’t do better than Coda. Truly beautiful code and CSS editor, with ftp, shell and reference books built in.

CSSEdit

Awesome CSS editor. Point it at a web page and see exactly what your styles are doing. Has saved me from going mad on more than one occasion.

TotalValidator

Standalone application or web-based service that validates and spellchecks web pages in one fell swoop.

Color Schemer Studio

Colour scheme designer. Can do funky things like create a colour scheme from a photo you provide.

Symbol Caddy Dashboard Widget

Keep all those awkward HTML entity codes at your fingertips.

Corporate Ipsum Dashboard Widget

Don’t have your web copy written yet? Generate as much lorem ipsum text as you want, right from your Dashboard.

PHP Function Reference Dashboard Widget

All the PHP documentation in a nice widget on your dashboard.

Writing

Scrivener

Possibly the best invention for writers since the pen. For drafting, outlining and research. I use this for drafing web content, articles and fiction. If you write, give it a try.

NeoOffice

Port of OpenOffice to the OS X, with a more Mac-like look and feel. It’s as good as OpenOffice gets on a Mac. So if Pages and Numbers are just too pretty for you, give it a try

Reference Tracker

Keeps track of citations/references for writers; easily add references from web pages or using an ISBN lookup. Handy, nice interface, still in beta but definitely usable.

Blogging and Social Networking

XJournal

LiveJournal blogging client.

MarsEdit

Blogging client for multiple platforms, including WordPress and Movable Type.

Twitterrific

Twitter client.

Pukka

Fast, light, multi-account del.icio.us client.

Chat

Adium

Multi-protocol instant messaging client.

Skype

If I have to tell you what Skype is, you probably don’t need it.

RSS

NetNewsWire

RSS newsreader that can sync with Google Reader, and from there with FeedDemon on Windows, or iPhone RSS clients like Byline.

Productivity

Evernote

The slickest note-taking system on the internet. Capture notes easily, from text, from websites, from photos. Save, read and sync them on the web, and from Mac, Windows and iPhone clients. It’ll even recognise words in photos you take and make them searchable.

Spanning Sync

Two-way sync of iCal and Google Calendar, and Address Book and GMail contacts.

TextExpander

Save your fingers by creating typing shortcuts for all your favourite phrases. Mac-wide macro replacement.

Books

Delicious Library

Scrumptious book cataloguing software. Can read barcodes using your Mac’s builtin camera and find the book’s details without you pushing a button!