I’m going to also add for photo editing check out GIMP (stands for GNU Image Manipulation Program). Its free & available for all OS platforms and is similar to Adobe Photoshop. I usually stick with Photoshop, but my BF swears by GIMP…
Also – I second Allison’s recommendation for Open Office. 1- Its free 2- it has a word processor, spreadsheet, graphics, database access, pretty much everything you need to start up / run your business without the cost or worry about licenses. Its pretty compatible with regular commercial office software too.
Google has a beta verison of Google Docs – a web-based word processor and spreadsheet, which allow you share and collaborate online, which might be worth a look thru (its also free). Use your gmail account to login.
— and as a note to the Open Source community – check out Linux’s Ubuntu OS – it might not be for everyone depending on your business, but it is free & certainly keeps the viruses at bay… (click here for the about Ubuntu page)