I grabbed one of these cheap USB to Ethernet Adapters off Amazon.com a few weeks back and it's worked great. The $5 shipped price tag leaves no complaints from my wallet either. It's obviously a hunk of plastic but it's solid enough and shouldn't give you any issue unless it takes a direct blow. Setting it up on my Cr-48 and Samsung Series 5 couldn't have been easier, it's plug and go. When you have it plugged into the USB port and an Ethernet cable connected, the Wireless icon at the top right of your screen changes to a wired port and you're connected.
Honestly you can't go wrong with one of these for $5 and it makes a great addition to your bag for when you're faced with finicky wireless and just need to get connected and working. If you prefer a brand name, you can also spend $30 on a Linksys USB Ethernet Adapter which is what Google apparently uses and might give you a little better performance and quality but for my needs, the $5 adapter is doing great.