I've never quite gotten a decent mental image of the relative sizes of the planets. Go here:
The Size Of Our World for a larger version of the pic at right, and others that will help develop that mental pic. Excellent!
(It appears that the site is blocked on some filters. I'll try to upload the pic directly tonight. It's quite impressive. Oh, also, it turns out that if Antares were to replace Sol, even Jupiter would be engulfed by the star. Sheesh! That's one big mother star!)