1,093 mp3 songs at 128kbps rate = 4 GB
I used to have over 1,500 during the Napster days, but lost it when my computer crashed or lost the burned CD's for it.
All my songs stored in my iPhone 4, Pixi Plus, PSP (with 32 GB card), VAIO laptop, CD-R's, Amazon Cloud, and Google Music Beta. Sold my iPods last year. I am a bit more picky on what to add. If I combined all the songs I used to from before with the songs I have now, I'd have maybe about 3K. But I am content with keeping it more limited to keep the storage usage lower and sometimes use the TuneIn Radio app or Pandora in case I get bored of my songs.
I manage all my songs with iTunes, MediaGo, and Zune software to prepare myself of getting an WP7 phone. And also drag and drop for my Pixi Plus because I hate DoubleTwist which gives me random duplications of songs.