Have you considered a used "touring bike"? They're made for racks, baskets, fenders, etc. Plus, you get appropriately low gearing for hills and loads. They're based on road bikes, so they aren't going to support very fat tires, but most can accomodate tires upwards of 1.2-1.5". Because they're designed to carry everything a person would need while riding a bike cross-country (I personally know folks who have ridden theirs across the US or large portions of it), they ride better loaded than a regular bike, the handling is more predictable, etc.
If you can swing the extra $400 or so, Surly sells their "Long Haul Trucker" frame built up as a complete bike for just under $1000, but I've seen them on sale for less than $900. That's a helluva bargain considering the frame is about $400 alone (that's what I have).
You should be able to find other brands of touring bikes used on Craigslist, eBay, bike shops, etc. Just do your research because some folks will call a bike a "touring bike" and it really isn't one.
Look for bikes such as the Trek 520, Surly Long Haul Trucker (aka LHT), Cannondale Touring 1 (and 2), etc.
Here's one from Bikesdirect for $599:
http://www.bikesdirect.com/products/windsor/tourist.htmThe LHT from BD for $929:
http://www.bikesdirect.com/products/surly/longhaul.htmBikedirect's prices include shipping.
Chris
