Hope you like lists...
Bars:
- Sala Equis: (Cinema bar- busy but definitely worth a visit)
- Cuevas de Sesamo : Sangria in a basement with a piano.
- La Venencia - "The one bar you must visit if you come to Madrid". A sherry bar. Looks like a working museum. No photos allowed.
- Daaraji: Senegalese bar/textiles shop in Lavapiés. Hypnotic furnishings.
- El Pavón: Bar attached to a theatre in Lavapiés with a beautiful wooden ceiling. Lot of artists and actors.
- El Mercado San Fernando: Unlike the best-known mercados in Madrid this one isn't expensive. Very busy on weekends.
- Barbieri : Parisian-looking bar in Lavapiés. Wrought iron columns, chequered floor, red velvet sofas. Great at any time of day/night. (Bar Manuela in Malasaña has a very similar vibe but with a big collection of boardgames).
- Lamiak: Basque bar with two locales in Lavapiés and La Latina. Incredible pinchos (vegetarian and fish options available).
- El Mercado San Fernando: (as mentioned above). Food from all over the world, reasonably priced and very good. If you're a meat eater visit El Rincón De Manolo for Asturian steak/other delicacies.
- Croqueta Solo: Croqueta-only restaurant in barrio de las letras. Relaxed, good place for a quick bite.
- Canastaco:Brilliant Mexican taco restaurant in a mercado in Delicias (close to Madrid Río). Not well-known yet. Excellent meat options but very little for vegetarians here.
- Bombay Blue: At the end of calle Miguel Servet in Lavapiés. Best curry restaurant in Madrid.
- Los Tres Cerditos:Famously popular Chinese dumplings. One location in Delicias and the other in La Latina.
- El Retiro: Goes without saying. It is a must-see.
- Templo De Debod: Slice of an egyptian temple given to Spain after an international UNESCO project. They mounted it facing the sunset and it's a good walk to combine with the palace and the cathedral. Lot of people visit at sundown, musicians etc.
- Parque Madrid Río: A riverside walk/park that stretches for a few kilometres. Can be combined with a visit to La Capilla de Goya and El Mercado Puerta del Angel.
- Parque El Oeste: By Moncloa at the end of Metro Line 3. Just as well landscaped as El Retiro but with half the visitors. Perfect for picnics. I actually have a friend who gives a brilliant historical walking tour of Madrid, focusing on this park and the surrounding area in the time of the Spanish Civil War. Link.
- Casa De Campo: Former royal hunting grounds. Covers a gigantic area and shows you a more realistic example of the natural tree species of the area (a lot of quercus ilex, for example). Also has a lake and some (expensive) bars.
- Parque Tierno Galván: Another favourite. A park in Delicias next to El Museo De Los Motores. Mix of industrial open spaces (train tracks, water towers, coliseums) and manicured lawns with fountains. Great for a medium sized walk. Keep an eye out for the abandoned imax cinema.
- La Reina Sofia - Free every day for two hours, I think between 7 and 9pm.
- El Prado - Free every day for two hours, I think between 6 and 8pm.
- El Thyssen - Free on Mondays between 12 and 4pm.
- La Capilla Pintada de Goya - This isn't known anywhere near as much as it should be. It's a chapel painted by the artist Goya. It’s also where he is buried, and it's free to visit.
Volunteering:
- Workaway: is a database of hosts looking for volunteers to work for them in return for food and a place to stay. I used a similar scheme called WWOOF in Japan for a year. The advantage of Workaway over WWOOF is that membership is global and lasts two years (WWOOF membership is on a country-by-country basis and usually lasts a year).
- Festivals: I’ve volunteered at a few festivals over the years, including Nowhere (Aragón), Traena and Karlsøy (both in Norway). Wherever I go, I keep an eye out for festivals looking for volunteers.
- Sea Shepherd: I haven't used this myself but a friend of mine just came back from working as a chef on a boat in Antarctica.
- Hitchhiking a boat: This is a fairly comprehensive guide to finding a spot on a boat (spoiler: difficult but not impossible), and covers different methods, networks and websites.
- Ridesharing: Very popular way of getting around in Europe. Blablacar is probably the most well-known and reliably widespread rideshare company in Europe. But when in France I try to use Mobicoop since it is a co-operative system where passengers are not charged the VAT and service charge that Blablacar charges.
- Trashwiki:A crowd-sourced database of the world’s uneaten food, in varying states of availability. I recommend reading the preservation tips first.