101 Hotel Bar, Hverfisgata 10. The bar at the 101 Reykjavik Hotel is worth mentioning. Very stylish, high class clientele.
22, Laugavegur 22. Bar on the main street, with a small dancefloor on the second floor. Once very popular, but starting to pick up again, especially after other places close on weekends.
Amsterdam, Hafnarstraeti 5. Has nothing to do with the Amsterdam, Holland. But open every night, bear and live music. Variable Entrance fee on Friday's and Saturday's.
Apotek Bar, Austurstræti 16. The bar at the Apotek Bar and Grill is quite popular to start the evening at with a view over the stylish restaurant.
Club Bohem, Grensasvegur 7,  is an exclusive night club in Reykjavík in Just about seven minutes drive from city center.
Celtic Cross, Hverfisgata 10. Traditional Celtic bar with wooden tables, chairs and fitments.
Dubliner, Hafnarstraeti 4. Traditional Irish bar with wooden tables and floor. A popular place for an evening pint of Guinness or a beer (500kr). There's also a decent selection of whiskies.
Felix, Þingholtsstræti 5. A sportbar with large TV screens for sport enjoyment. A large dance floor with DJ playing on weekends.
Gaukur á Stong, Tryggvagata 22. In the heart of downtown Reykjavík there is a club that is open every night. All evenings there is a band playing live music and people having fun. This place is called Gaukur á Stong and has been running for over 18 years in complete success. It´s the only place in the city where you can be guaranteed a party atmosphere every night of the week. Variable Entrance fee.
Glaumbar, Tryggvagata 20. The Reykjavik "Cheers" as in the movie, this is one of the few bars in Iceland thats been able to get the barfly culture going. Well worth checking out.
Hotel Ísland, Armuli 9. The larges disco in Iceland, Broadway, known for Vegas-style shows, singing and dancing spectaculars, though occasionally with more interesting fare and popular with people of all ages, from teenagers to pensioners. Variable Entrance fee.
Hverfisbarinn, Hverfisgötu 20. I hip bar that turns disco on weekends. Very popular with students.
Hressingarskálinn (Hressó), Austurstræti 20. One of Reykjavik's oldest establishments is back with new owners. A very international atmosphere, board games, good reading material and good food. Free wireless internet. Dancing on weekends.
Kaffi List, Laugavegur 20. Has made its name through the years featuring Latin and World music themes. Has a dancefloor that is used on weekends.
Kaffi Reykjavik (Cafe Reykjavik), Vesturgata 1, Don´t let the name fool you, it´s smack in the middle of Reykjavik, big restaurant/bar, everything for everyone - At Kaffi Reykjavik you can find the home of the famous Icebar.
Kaffibarinn, Bergstaðastræti 1. Part owned by Damon Albarn of the english group Blur. A very small and often packed bar popular with the icelandic bohemian crowd.
Kaffibrennslan, Pósthússtræti 9. One of the most popular bars in Reykjavik with the biggest variety of beers in Iceland. Great varied menu. Warm atmosphere.
Kapital, Hafnarstraeti 17. A popular young nightclub. Techno and Hip Hop. Popular also with the capital's gay population on Friday and Saturday nights.  
Klúbburinn (The Club), Storhofda 17. Not in the down-town central but pretty cool sport bar that shows life feed from sport events like UK, German, Italian, Spanish and Dutch Footbal (soccer), Forumal 1, American footbal, NBA and more. On week ends there are life bands. 
Mojito, Pósthússtræti 7. A very popular, stylish nightclub in the heart of Reykjavik. Situated on the 5th floor above the Apotek Bar and Grill this club is only open during Summer. During winter it is only open to private parties.
Nasa,  by Austurvoll. The largest club in downtown Reykjavik. Live bands on weekends and a disco after midnight. The second floor bar opens at 23:00 and the nightclub itself opens at midnight. Entrance fee is 1000 kronur.
Nellys, Þingholtsstræti 2–4. American-style bar with a mixed gay and straight crowd, especially at weekends, open till 1am daily and serving Iceland's cheapest beer, about 300 Ikr for 5mm ml. glass – so it´s understandably popular.
Pravda, Austurstræti 22. Cool nightclub full of wannabe yuppies having fun and dancing to the latest sounds on the upstairs glass dancefloor. No jeans or white trainers allowed. Variable Entrance fee.
Odal, Austurstæti 12. The only erotic club in downtown Reykjavik. A high-class club, stylish and relaxed. Reykjavik and Iceland laws are very strict on erotic clubs.
Prikid, Bankastræti 12. One of Reykjavik's oldest bars. Very small but seems to pack in a lot of students. DJs on weekends.
Sirkus, Klapparstígur 31. Reykjavík's first French wine bar, in an unprepossessing building off Laugavegur. French wine is available by the glass, as is pastis and calvados. Busy at weekends with a Bohemian clientele who don't mind queuing to get in.
Solon, Bankastræti 7a. A very good restaurant/bar/coffeehouse. A rocking nightclub for young people with dancing upstairs on weekends. 
Vegamót, Vegamotastig 4. One of Reykjavik best keept nightclub secret, known to be a great restaurant this bar also turns nightclub on weekends with many of Icelands best DJ's turning their tricks in a non stop party. Food is served from noon until evening every day and as the night progresses the atmosphere starts to change and the crowd with it as Vegamót evolves into a wild nightclub.
Vídalin, Adalstraeti 10. One of Icelands oldest house and oldest pub, offen live music in thursdays and even fridays and saturdays, but mainly disco. Variable Entrance fee.
Victor, Hafnarstræti 1-3. Situated in a historical building downtown Reykjavik. A bar with good menu. Very mixed, international customers. 
Vínbarinn, Kirkjutorgi 4. Behind the National Church and the Althing. A great wine bar. Popular with Icelanders of all ages.
Thjódleikhúskjallarinn, Hverfisgata. Despite its strange and unpronounceable name, the basement cafe underneath the National Theatre transforms itself into a popular club playing 1970–80s music on Fri and Sat nights (midnight to 3am).
Thorvaldsen Bar, Austurstræti 8. One of the most popular nightclubs in Reykjavik. A good restaurant/bar that changes into a great nightclub on weekends. Eighties music mixed with new. Very difficult to get into if you get there late. 
Ölstofan, Vegamotastig 4. The full name is Ölstofa Kormáks og Skjaldar and this is watering hole for a lot of famous icelandic actors, TV personalities and musicians. No dancing but a lot of drinking and smoking.