That's cute. ABBA's "Ring Ring". The White Stripes' "My Door Bell". Talk Talk's "Talk Talk". Yaz's (Or Yazoo's, depending on if you're in the UK or the States) "Bad Connection". Silver Scooter's "Tribute To The Phone Calls". Tom Waits's "Telephone Call From Istanbul". The Straford 4's "Telephone". The Be Good Tanyas' "Broken Telephone". Those should give you a start, anyway. Bear in mind I haven't checked those to see if they are iTunes ringtone-approved and I own a lot of them from CDs so iTunes won't let me use them.
I'm using Tennessee Ernie Ford's "Sixteen Tons", which I already bought from iTunes and was surprised to find was ringtone-friendly. Used to use the theme from the 1970s "Sanford and Son" TV program on a Nokia phone -- look at my user name; that's my real name -- but I haven't checked to see if iTunes has it available for ringtones. I'll probably buy about 10 ringtones and then the thrill will be gone, but it's a very elegant little ringtone-purchasing solution with a much wider and diverse variety -- I mean come on, Ford's "Sixteen Tons"? -- than you'll find with any mobile carrier.
Face it: the best ringtone for an iPhone is the Alarm ringtone personalized for your boss, mother-in-law, substance abusing cousin, money-borrowing kids, ex-wife or ex-husband (or unmarried versions of each) or whomever.