I released a free app on Android Market called Pubtran London (it's a London journey planner), what are the best ways to promote it? I mean besides posting about it here ;-).
Users who want the functionality my app provides probably already use some other app, that is possibly worse than my app. How can I make them switch?
Start a blog or if you have a blog already, write about it on your blog. Then, submit it to Ycombinator, Reddit, places like that (you know what I am talking about). You will find many people there who have a strong voice (bloggers, other enthusiasts) and would like to review your app. That is half the job done (i.e. spreading the word). For the rest, sit back and relax and see what happens. :) Another thing, consider submitting it to markets other than the Google market. Finally, ff your app is good, it will be spotted. Only takes some time. This is the least you can do to reduce that time.