If the content is in a content database with no other content, you could backup the content db and move it and then attach it in the new farm.
If it is not, you can use the command line
stsadm.exe -o backup -url [yoursitecollectionurl] -filename [filename]
to back the file up on the current server, then copy the file to the new server and use the command line
stsadm.exe -o restore -url [newsitecollectionurl] -filename [filename]
to restore the file to the new location. One caveat to this is that you must have the new web application created on the new server farm. You don't necessarily have to have the new site collection created. However, if you have created a blank site in the same url that you want the new site collection to be restored to, you will want to add
-overwrite to the command line.