lame is normally used to encode mp3's, but it can be used to decode mp3's to wav files which is what's needed for audio cds. i don't use gnome-toaster, so i don't know how it goes about it. but reading the features of gnome-toaster, i doesn't say anything about burning mp3's to audio cds. the only thing i found relating to that was encoding mp3/ogg/wav files and a preview play of music before you burn a cd. if gnome-toaster doesn't decode mp3's to wav files on the fly for burning, there's a few of ways you can go about decoding manually using lame. all basically involve a shell terminal. the first way is to do the lame command individually for each song you want to burn, but who wants to do that? another way is to right click on a mp3 file on your hard drive and choose the Edit filetype option (depending on your desktop environment, you'll have to dig around on how to add programs to a filetype. kde let's you right click on a file and there's an Edit Filetype option from the context menu).
anyway, associate this command, "lame --decode", with mp3 files and make it an available choice when right clicking an mp3 file. then you can just select mp3 files from your file manager like normal, right click it, choose "open with > lame" or "open with > lame --decode" depending on how your desktop environment names these kind of program/filetype associations.
the only drawback is if you have mp3 files on a non accessible directory (you don't have read or exec permissions) because it will try to write the wav files in the same directory as the source mp3 files.
i use x-cdroast myself and have to manually encode mp3 to wav files. so this brings us up to a third way of decoding mp3 files to wav files. i wrote this little diddy, lame wrapper program that handles that. you can choose the target directory where the decoded wav files will go and yadda yadda yadda. it's written in java version 1.4.1_01 so you'll need to have at least the java jre installed, the path, and JAVA_HOME environment variable set. anyway, if you want it, here's the program:
if you have java all set up, then there's no installation. just unzip the zip archive anywhere on your hard drive and create a shortcut to the java command.
unzipped in /home/user which the directory, mp3-wav, is extracted to -> ie. /home/user/mp3-wav
create a shortcut and set the execute command to:
java -cp /home/user/mp3-wav/classes mp3_wav.mp3_wav
wav files are stored by default to your user's home directory, but you can specify any directory where you have write access.
here's the source code if you want it.
mp3-wav converter source code
of course if gnome-toaster does decode mp3 files on the fly, then just ignore this post and pretend i never posted. you could try other cd burners too like e-roaster or k3b which to my knowledge will decode mp3 files on the fly. i just use x-cdroast because that's the only thing i could get working on my system.