The Beatles - almost the whole catalogue of Beatles tunes is well worth learning. For beginners, Hey Jude, Let it be, Rocky Racoon, Norwegian Wood are all fairly easy. Most public libraries will have songbooks, just work through any songs you like.

Leonard Cohen - Famous Blue Raincoat. This is a great song, and works well with a simple fingerpicking guitar part (see original recording) I've put in a link to a different interpretation, by Jennifer Warnes - because for me it's the best version. Generally, the best songs will work with just one guitar and vocal part, and this is a good example.

Most Leonard Cohen songs will work well with a minimalist approach, as they are essentially poetry set to music. When you listen to this the verse is in a minor key, and the chorus is in the relative major, so there is a real lift for the chorus and a change of mood. If you're striving for an authentic version, play nylon-string guitar on this one. If the pitch is wrong for your voice, try a capo at fret 2 or 3. Doing this often brightens up a guitar's tone and makes it easier due to the smaller fret size and lower action.

Also by Leonard Cohen: Suzanne is a song featured on James Taylor's album "Covers" in a very tasteful version. It's fairly easy to play a nice fingerpicking part for this song.

Dylan songs - Knockin' on Heaven's Door, Like a Rolling Stone. She Belongs To Me, Hey Mr.Tambourine Man are all quite easy - and great songs.

Below is my affiliate link to Acoustic Guitar magazine - a great source of songs and lesson material.

Another simple, but great, guitar/vocal arrangement from one of the best albums of all time, Blue. In conversation with other musicians we all agree it's something special. This song is in open G tuning, a very versatile tuning. More detail is on my hub- Guitar in open G tuning. Check out my hubs for more Joni material. At the bottom of this page there is also a link for DVDs - Woman of Heart and Mind is really good,and at $3 Refuge of the Roads has to be the best musical bargain ever!

Many great songs are transcribed at jmdl.com (link below) which is a great site.

Different tunings: DADGAD is also widely used, and is the subject of another of my hubs: Guitar in DADGAD tuning.

A great Bach - inspired guitar piece that sounds good in standard tuning as well as open G tuning. Also works well on piano. Excellent for Travis fingerpicking, and nice harmony that transfers well to many other songs - such as Willin' by Little Feat. A good example of "less is more" approach - as most of the time there are only 2 or 3 notes implying the harmony, which still sounds full and complete.

Sultans of Swing - Mark Knopfler. This song is full of great riffs, solo ideas and different techiques, and well worth learning.

Autumn Leaves - a good introduction to jazz guitar, with a great chord sequence that is perfect for improvisation.

America - Paul Simon. This is good for fingerpicking and improving chord vocabulary, and is one of dozens of songs that use descending bass lines to good effect.

12- Bar blues in E and A : the basis for hundreds of songs,blues, rockabilly, rock n' roll, funk. Therefore something worth learning inside out.

There are many guitar pieces that have become "standards" in a more informal way than the list of jazz standards. Here are some suggestions, many of which are in videos in my hubpages articles.

They are selected on the basis of valuable guitar learning material, and also being well-known and strong songs.

Stormy Monday
The Thrill is Gone
Sultans of Swing
Stairway to Heaven
Only Livin' Boy in New York
Don't think Twice, It's alright
Blackbird
Light My Fire
Little Wing

 I also think it's worth learning many of the songs from Eric Clapton's Unplugged CD and DVD, as this is almost a history lesson in blues guitar playing.