In real terms the odds of anything particular bad happening to any of us while we build Drupal websites and sell awesome fixies is low, as a matter of best practices and general sanity here are a few things you can do to keep your local workstation or laptop a little more secure.
1.) Make sure to use a secure/encrypted session to the company email.
There are generally two ways you can access your webmail account (see below for examples from our company) and while they look and work the same way there are critical differences. If you use the normal "HTTP" connection, the emails you are sending and receiving can be snooped/hijacked by anyone on your same wifi or cable modem network. You must use "HTTPS" to have a secure/encrypted session to the email provider making it more difficult to snoop on your traffic.
2.) Be aware that IRC channels are often *not* secure (same goes for private messages through IRC)
The IRC network as a whole is not encrypted and conversations and passwords that flow through it can be easily snooped and recorded. This is true not only for people on your local network, but also for server operators and people with some smart masking/spoofing skills. IRC is often full of very shady people. In general, IRC should not be used to communicate sensitive information or server passwords.
3.) Securely communicate with your colleagues and clients using AIM *with* the OTR
The best way to discuss sensitive topics or share server/login credentials is through AIM (AOL Instant Messenger) using a plugin called OTR (Off the Record). If both users have this plugin, their communication is encrypted and cannot be read by anyone else. Without this plugin, anyone can read your messages and all data goes through the AOL main network to be relayed out....
Main OTR Page: http://www.cypherpunks.ca/otr/
Adium - http://www.adiumx.com/ (included by default)
iChat - http://chris.milbert.com/AIM_Encryption/#MacOTR
Pidgeon/GAIM - http://www.cypherpunks.ca/otr/README-pidgin-otr-3.2.0.txt and http://www.cypherpunks.ca/otr/binaries/windows/pidgin-otr-3.2.0-1.exe
Trillian - http://trillianotr.kittyfox.net/downloads.php
4.) Encrypt Your Harddrive
There are lots of pieces of sensitive data on your harddrive - from server passwords to saved emails and logged IRC/AIM chats - that should be protected. The best way to protect this data, of course, is to keep your laptop under your control, but if the laptop is stolen or misplaced bad things can happen. A very simple solution is to encrypt your user directory so others cannot read that data (even if they steal your computer).
5.) Consider Locking Your User Session When You Leave
Along the same lines as encrypting your harddrive, its helpful to also "lock" your computer session when you are not using it. This is less important in the office or a trusted work space, but if you have sketchy friends or are in a public place locking your computer will prevent others from stealing your data or pretending to be you.