If I have a bunch of photos to move I'll plug it into my computer using USB and copy them that way.
When you plug it in you'll see an option int he notification tray on your phone to change the mode from "Charge Only" to "Disk Drive" (or something like that). Switch it to the drive option and you'll be able to browse your SD card on your phone.
Another is to use Dropbox and upload them using your phone. There's also an app WebSharing that allows you to browse your phone on WiFi from a browser on your PC and download files.
*Note: there's a free lite version of WebSharing available as well.
**Note: My referral Dropbox signup. If you do decided to use Dropbox sign up using this link and we'll both get an extra 250 MB.
Photobucket and Flickr are easy to use from Android. Set up accounts at both and upload directly to your albums. There's a good Photobucket app in the Market.
Yup, this is probably the simplest and most available way, since everyone has the the USB cable that came with the phone. Depending on the situation, however, one of the other options may be more convenient.
Other methods you can try (some already mentioned):
Take out the microSD card from the phone, and use an adapter for your computer.
Use one of the available apps in the market to turn your phone into a server so you can transfer files over wifi.
Email the pictures to yourself. Open the email(s) on your computer.
Connect your phone to your computer via Bluetooth. Make sure you've enabled "FTP Server" in the Advanced Settings for Bluetooth on the phone.
USB drag and drop is the quickest and easiest solution. As others have mentioned, there are alternative solutions, but if you don't have them already setup and ready to go it will take a bit longer to set it all up and offload your pics.