Have fun with it! The rhythmic feel should be very loose - you don't need to play it exactly as notated, it should be felt rather than read. It may be repeated a number of times. You can experiment with the tempo too, perhaps by starting slowly and gradually speeding up.
Tchaikovsky - Swan Lake Op. 20 Scene Finale
This is probably the most emotionally-charged melody from Tchaikovsky's famous ballet. It has been widely used in popular culture, perhaps most famously in the final moments of the film Billy Elliot:
Expressivity is everything in this beautiful melody. Make sure you observe every slur and articulation mark and leave enough space (i.e. don't start too loud!) for the big crescendo before the climax at B.
House of the Rising Sun
House of the Rising Sun is a traditional folk tune originating from New Orleans, USA. It was made famous by the Animals cover of 1964:
Listen to the original song before playing - it will help you to work out where the phrases are and thus where to breathe. Watch out for those duplets at bars 24, 26, 30, 32 and 34 - they should be played evenly against the triplet rhythms in the piano.
Beethoven Fur Elise
Originally for piano, the piece adapts beautifully for the clarinet:
When playing, ensure that the arpeggios split between the piano and clarinet (for example at bars 2 and 3) join together if they were one flowing movement. The section at bar 18 may be played with more movement. The transition back to the opening material at bars 23 to 24 should be played gradually more slowly before returning to the opening tempo at bar 25.
8notes also has a full version of the piece for more advanced players:
Notice how the soloist doesn't try to make the improvisation too difficult, instead concentrating on giving it a convincing musical shape, for example by marking its beginning with a long note and saving the highest note for the end:
You can also get some more ideas listening to the piece on 8notes before trying the improvisation - the full playback also contains an example improvisation.
Beethoven Moonlight Sonata
The opening of Beethoven's three movement Sonata No. 14 in C# Minor is another work originally written for piano that makes a great clarinet solo:
The key here is breath control - work out were the phrases are and breathe in the same place every time you practise. The clarinet should remain quite even in tone throughout, almost as if it were floating in space.
Pachelbel - Canon in D
Originally written for three violins and basso continuo, it has nevertheless become hugely popular piece for the clarinet. The key here is to set a steady tempo at the beginning and stick to it - it gets tricky later on, so if you've started too quickly you will soon regret it!
The melody was originally sung, so make sure that your playing reflects this. Phrases occur every four bars - breathe at the end of bars 4, 8 and after the third crotchet in bar 12. Play with a full but beautiful cantabile sound.
Mexican Hat Dance
Probably the most well-known mariachi dance from Mexico. It makes a great encore piece!
Be sure to observe the phrase marks when breathing but, at the same time, don't confuse them with slurs. Listen, for example, to Wang Tong's performance on flute - she uses quite an imaginative combination of tonguing/slurring whilst nevertheless observing the phrase structure.
Strauss II - The Blue Danube
Strauss's melody was already hugely popular before Stanley Kubrick's used it in his seminal film 2001. You may also hear it being played as part of the Vienna Philharmonic's New Year's Day concert at the Musikverien, Vienna. Clarinet versions of the piece have also become very popular.
An important feature is the shift in accent between normal 4/4 bars (bars 4, 5, 8, 11, 13, 15, 17 and 20) and the other bars which are based on dotted crotchets, two tied quavers and a quaver. Make sure the difference is clear.
This old Christian Hymn has become immensely popular, both in church and concert hall:
Breathe only at the end of phrase marks. You may use some soft-tonguing within the phrases though grouped quavers, including triplets, should be slurred, even though this is not marked. Be sure to try playing with the 8notes band backing, it's a lot more fun!
O Holy Night
If you are looking for a seasonal piece that is more interesting than your average carol, O Holy Night, written by French composer and critic Adolphe Adam in 1847 is an excellent choice. It has been widely covered, for example by Mariah Carey in 2009:
The first two phrases (bars 2-6 and bars 7-11) are separated by rests. Each should be played in one breath. Thereafter breath marks are shown. Though the dynamic shape is indicated, with the high point at bar 37, you might also think of adding your own touches - e.g. the new idea at bar 12 could be emphasised with a louder, warmer sound whilst a crescendo towards bar 20 followed by a diminuendo to bar 23 would also be very effective.