Search Tools and Internet Information

Scroogle - Google search without the tracking and the logging

Weather Underground - Free weather reports

Time and Date.com - pretty much exactly what the title would lead you to believe

Babelfish Translator by Altavista - translate blocks of text and web sites

Dave's HTML tutorial - Great (free) online tutorial covering the basics of web design , up to advanced topic such as CSS

Freedom List  - Directory of free and cheap dialup Internet access worldwide

Public Libraries on the Web - Find a library w/ Internet access in the United States

WorldCat - Search for a particular book in all libraries near your location. Searches public city library indexes as well as private universities

Yahoo Directory listing of alternative newsweeklies (U.S.)

Peacefire.org - Learn techniques to circumvent Net Nanny and other obnoxious censoring filters

Simply Google - All Google's search stuff and other toys condensed into one page

BoingBoing Guide to Evading Censorware

So You Wanna? - encyclopedic general information site

LibrarySpot

RV Internet Access - don't necessarily need to be in an RV to make use of this :)

Camping / Hiking / Travel Knowledge

Knots and Knotting - A Boy Scout site that describes (with step-by-step pictures) how to tie a variety of useful knots

NGA Raster Roam - honestly, i added this over a year ago and i can't remember why. i think you can look up latitudes and longitudes.

BootsNAll Travel Network - general purpose vagabonding site

Wilderness Survival Handbook by Alan Fry - Though this is focused on survival in the arctic North , there is plenty of general purpose useful information on direction finding , brush shelters ,
 snares , clothing selection and other such for anyone in any climate. Used copies of it are extremely cheap and easy to find.

Practical Advice on Boat Hitchhiking

Bushcraft UK - UK wilderness/survival site, but with lots of practical info for any sort of locale

Plants for a Future - Edible, medicinal and otherwise useful plants

Natural Health School

The Thru-Hiker's Field Medical Guide

Shipping / Storage / Misc. Gear Issues

Sending mail General Delivery (U.S.) - Link to Post Office page, way to send mail and have it held at a Post Office for pickup for up to 30 days

Hold at FedEx Location - Another option for mailing stuff to yourself when you have no mailing address. You can ship it by FedEx Ground and have it held for pickup at any Kinkos location, for what looks to be at least 5 days.  Looks like UPS does the same thing as well - these may be better options than the Post Office as you can track your packages online and make sure they didn't disappear mysteriously.

Homeless-Specific Help

Survival Guide to Homelessness - personal journal and tips, though it seems to have ceased to be updated about a year ago. advice is geared more towards vehicle dwellers in large urban areas.

Flex Your Rights  - Information on handling police stops and searches. EDIT : Advice from yuppies who admit they have never actually been stopped by police on how to handle police stops. However, you may still learn something useful here, though don't expect things in real life to work out exactly the way these guys present it.

Digihitch / Great Campfire Forums - Forums centered around the hitchhiking culture, lots of advice however for general purpose hobos, homeless and nomads of all types

211 - Emergency number in United States for human services needs (not active in all areas - check website)