Just couple lists of .com domains with few patterns to choose from.

If you are starting an another project or wish to invest in domains maybe you will find something of use.

State Trend is monitoring reddit for new posts to research on.

With State Trend you can see how is your keyword trending over time and determine what are the current topics around.

Google trends can tell you what are people searching for but InsighTrend tells you what are people writing about. You can discover what is trending around your keyword or topic and see what people hate or like.

A simple list for people that would like to work on an idea or app which is already validated by users, because they pay for it. One can than narrow the list by rating, price or usage