to get things going to practice for a job to practice a grammar point
Sometimes all you need to get a good discussion going is a "launch pad". There is tons of great content out there that create great speaking material. I am sharing some of my favourite "go to's" for breaking the ice or even getting down right philosophical. I try to stay away from conversation prompts that are too litigious. I look for topics that can interest almost anyone. If you use videos, articles or podcasts, you might want to check out my Tell Back and Questions by Cognitive Skill tutorials. These techniques are a good way to deepen the pedagogical impact of the conversation and make sure that you get everyone's full attention (there is no room for doing your shopping list when someone else is talking).
Open-Ended Questions
Conversation Starters
First language site with a huge array of ice breakers, philosophical questions and light heart discussion topics
New York Times 163 Questions to Write or Talk About
First language ressource with many thought provoking questions
Getting to Know Someone
Getting-to-know-you questions
Philosophical Questions
For your philosopher/reflective students
Deep Conversations
Also for the students who like reflective/psychological topics
Ice Breakers 
Some fun and some weird, a collection of questions meant to warm up discussions.
eslconversationquestions.com
An endless list of topics for conversation. Simple enough for ESL but interesting enough to stimulate adults and young adults.
Busy Teacher
Hypothetical situation meant to fuel creative writing in first language students, but also work for discussion
eslwriting.org
This is a fantastic ressource for ESL and Language Arts teachers. A bit like this site, Rob feeds a regular lesson blog with videos, texts, questions and printables.
Print and Discuss 
Just as the title implies, this site create discussion questions on a variety of topics. Simple and easy on the eyes, there is a good variety of topics. And that's all they do, so you really can't get lost on this site.
Brainfall
Fun silly personality quizzes on all kinds of topics
28 ESL Discussion Topics 
Some of these topics are also on the other sites I have referenced, but for the sake of variety, these are quick discussions that can spark the esl discussion flame.
The Only List of Icebreaker Questions you Need
Although these ice breakers claim to be for corporate team building, they are general enough, cooky even, for classroom use or for one on one lessons.
Video and Talks
Watch my video to see on how I use the "Tell Back" technique with video and podcast material
10 talks you won't be able to stop thinking about
Mostly 20 min long presentations that can be broken up into segments. Great material to react to. Something for everyone.
New York Times Video
Short news broadcast, some with close captioning. They are fast, but can be used as a good launch pad.
CNN-in 10
10 min broadcast of the daily news. They are fast, but supported by images, so lots of visual context.
eslwriting.org
If you can write about it, you can also talk about it. ESL writing.org is full of great thought provoking prompts. Here I am linking the video prompts section, but there is so much great stuff on this site, it's worth taking some time to go through it.
Crash Course
Basic business vocabulary, chemistry, history, politics, internet security, you name it, Crash Course has got it. This YouTube channel features 10 min basic instructional videos on just about anything you can think of. The speakers can be fast talkers, so I suggest turning on the CC feature and slowing down the video.
Photos and Images
Watch my video on how to calibrate the difficulty of the discussion with the "Question by Cognitive Skill" tool.
What's going on in this photo (New York Times)
Thought provoking photos that are rather nebulous, so lots of guessing and hypothesizing.
National Geographic's Photo of the Day
Stunning photographs from around the world. Some of nature, some of society, some thought provoking, some meditative. You can practice action verbs, descriptions, colours, description of people, clothes...so much can be done with photography.
50 Photos for ESL discussion
Fellow blogger and ESL teacher Jeffrey Hill offers a great slide show full of action packed photos to use for discussion.
Podcasts
The Daily
New York Times podcasts. Reporters speak relatively slowly and clearly.
CBC Radio Podcasts
I have yet to find an ESL pearl among all these shows, but I thought I would share anyway in case there is one for you.
Additional Ressources