A most wonderful and relatively comfortable and easy trek through the very diverse landscape around the Annapurna massif at the heart of the Himalayas. The views during dry season are stunning, and the local people are almost unbelieveably nice and friendly. I can absolutely recommend doing this or a similar trek. See also my trek in the Everest region a year later.
The only complaint I had was about the Maoists, who until 2008 forced tourists to 'donate' approximately 1€ per trekking day for subsidizing their activities. This phenomenon is meanwhile gone, but here's a more serious nuisance: due to road construction starting even before 2007, meanwhile large parts of the circuit are accessible by jeeps and buses, so much of the quietness is gone :-(
See the Wikitravel: Annapurna Circuit for more up-to-date information.
For geographical information, you may use my Google Earth placemark or the interactive map below. The trail from Besi Sahar to Phedi is about 250 km long (with a total of about 13000 m of ascent), or some 300 km long when including the side trip to the Annapurna Base Camp. Further detail can be found for example on Ian Johnson's online guidebook.
Our journey was co-organized by the Austrian Christian mountaineering operator Leben Extrem and the Nepalese trekking company Eco Trek.
Before and after our trekking tour, we spent a couple of days in Kathmandu and its vicinity.
Day 1: Besi Sahar to Bahundanda
Day 2: Bahundanda to Tal
Day 3: Tal to Chame
Day 4: Chame to Pisang
Day 5: Pisang to Manang
Day 6: Manang (rest day)
Day 7: Manang to Yak Kharka
Day 8: Yak Kharka to High Camp
Day 9: High Camp to Muktinath
Day 10: Muktinath to Tatopani (in a rush)
Day 11: Tatopani to Ghorepani
Day 12: Ghorepani to Chuile
Day 13: Chuile to Sinuwa
Day 14: Sinuwa to Landruk
Day 15: Landruk to Pothana
Day 16: Pothana to Pokhara