Amazon - Kindle now US$189
Anyhow.... US$189... ($209.98 inc delivery). That's about $250 here in Oz.
File support includes Kindle (AZW), TXT, PDF, Audible (Audible Enhanced (AA, AAX)), MP3, unprotected MOBI, PRC natively; HTML, DOC, JPEG, GIF, PNG, BMP through conversion. 1.4Gb space on the thing - which doesn't seem a lot, but ebooks are not big.
You can get something like the Kobo from Borders (http://www.borders.com.au/ereader/) for $199 - well, when they get stock. But that doesn't come with the convenience of 3G.
By the way, to convert books to .mobi format I recommend http://calibre-ebook.com/ (free and mac/windows/linux versions)
Oh, and also at the moment you can get the Australian charger (a standard power adapter with a USB port along with a cable) for $4.99 ($15 discount)