If you're hard wired to the router (i.e. not using wireless/802.11), you are slightly more secure, as someone would have to compromise a point upstream in the Internet to read your traffic. That's not impossible, but its much harder to crack a Telco or ISP router than it is to capture packets going wireless to an 802.11 access point 15 feet away.

Log on to public web sites via the HTTPS (secure) option if available. DON'T do banking or anything else critical if there isn't a secure option. Use VPN or SSL connections wherever possible.
If you must download email via POP or another "in the clear" protocol, you're probably OK if you are using a wired connection at home straight to a DSL router to your ISP, as the only compromise points are at major ISP/telco locations that are generally well monitored and secure. Having said that, I wouldn't do it myself.

On the other hand, I'm posting this via unencrypted wireless to an 802.11 AP, but if someone did sniff it all they'd get would be my flyertalk logon/password. Not a big deal.

That brings up another good security point. DON'T USE THE SAME PASSWORD EVERYWHERE. Especially don't use the same password at secure sites (like your bank) and insecure sites (like this chat room). If someone gets your password from one site, they'll try it at others.

Bob
PS: I know I'm vastly oversimplifying everything above, but it would be much too complex to explain really good Internet hygiene here. But if anyone's curious, I've been a 'Net user since it was the Arpanet running POP instead of TCP/IP, and I've been building network management and security products since 1988, so I really do know what I'm doing, even if my posts don't make that clear :-)