For secure browsing, you can use a proxy service, but you can't be sure the proxy is trustworthy. It could be a honeypot. Or it could be legit, but they'll turn over their records under court order. Best bet is to use Tor/Vidalia.
For secure file storage, you'll want to use full disk encryption. You could pay for PGP's product. But there is also Truecrypt, which is free and just as good. Of course, the courts could compel you to give your password. To get around that, you would use a hidden operating system. Basically it's an encrypted OS within an encrypted OS. They'll know the first one is there, and you can give the password to that if compelled, but they will have no way to prove the second OS is there (as long as you follow certain rules (deniability for anything you do is of utmost importance)). Use the hidden OS to hide all of your super secret stuff.
If you need to securely erase files, get Eraser (
http://eraser.heidi.ie ), but this should only be done when full disk encryption is not an option, or if you didn't realize you should be using it.
For secure email, use something like Thunderbird with the Enigmail plugin. You're looking to use what's called Public-key/Private-key encryption and signing.
For secure IM, use Pidgin (for Windows and Linux), with the Off The Record plugin (there's an Encryption plugin, but it's not as good). If you have a Mac, you can use Adium, which comes with OTR built in.
With any form of communication, you need to realize there is a risk from what's called a Man In The Middle attack. Learn how to defend against that. Also, you can't always be sure who's reading on the other end, or who's sending, if the other party has been compromised. That's just part of the risk. Find your own creative solution to this (e.g. secret authentication code).
For secure VOIP, use ZFone (make sure your VOIP software will work with it).
For all online stuff, use SSL where possible/applicable.
Don't trust Skype, Hushmail, or any other service that claims to offer encryption. They're either not very secure, not trustworthy, or can be compromised by court order. Your best bet is to stick with what I listed above.
Never ever say anything incriminating over the phone. Ever. No hints. Be careful with code words. You can get encrypted cell phones, all parties in a call must be using them. I won't recommend these as I've not looked into them too much. The contents of your conversation may be safe, but the record of the calls isn't. And don't even think about using text.
Be careful what you say online. Anything you write will give Them a better idea of who you are. What seems like innocuous conversation online, even with all the security measures in place, helps Them build a profile of you, if they become interested in you. They'll be able to narrow down where you live, your gender, approx how old you are, what your politics are, what kind of work you do, your hobbies and interests, etc. This isn't much by itself, but if they think they have other info on you, this stuff will help corroborate that. I don't mean to sound paranoid... I'm not high right now, and haven't been for quite some time... few of us would do anything to warrant that kind of attention.

Just want to give you an idea of how to protect yourself.
Hope that helps as a starter.
More details below:
https://ssd.eff.org/