I see Joe got in while I was compos(t)ing...

Sing Out! magazine has for the past year or so offered a CD of much of the stuff included in each issue of the magazine. You do have to pay a bit more for the subscription to get it along with the magazine. They were including notation for quite a few of the things in the mag; but we succumbed to the demands of poverty and let our subscription lapse a while back, so I don't really know what they're doing now.

Tunes, as opposed to songs, are available in lots of collections. Folk purists distinguish tunes as things ordinarily played without singing, and songs as things that ordinarily are sung (often without accompaniment). There's some overlap, so a tune book may give you tunes commonly used for songs, and words crop up to go with popular tunes. In my area, where there are lots of cowboy/bluegrass/wannbeirish players, the Fiddler's Fakebook is popular and has a fair selection. If you're more inclined toward old-time than bluegrass I like The Portland Collection.

A visit to "Mel Bay" or "Hal Leonard" on the web may find what you want, or may give you a better idea of how to describe the particular kind(s) of things you're looking for. They publish a lot of stuff, some with music notated and some with just words.

Note that Rise Up often gives "to the tune of" indications, and a list of the "tunes" in hand while you're looking might be helpful. You may also find .mid files of quite a few common tunes downloadable from the "Digital Tradition" right here at mudcat. A "paid subscription to mudcat" is quite inexpensive (i.e. free) if your mom is thinking of a gift. You can, I think, still download the DT database or, I think still get it on a CD(?). Check the FAQ here.

The summary answer is that there are lots of books available with tunes to songs; but the problem is finding the one(s) that suit your need.

John