One of the things that makes getting around Dublin by public transport difficult is the fact that there are three totally independent public transport systems, Dublin Bus, Irish Rail and Luas each with their own web site which contains routes and schedules. However, if you use the Hit the Road web site, you can simply enter where you want to go to and where you are starting from and it will automatically find the best combination of services to use. It will even give you an estimate of your overall travelling time including walking to and from the bus/train stops. If there are a few alternatives which are close to being optimal it will show each of them so that you can manually choose and it will include a helpful link to the schedule for each of the services it is recommending.
It is great to see private innovation helping solve real problems for the citizens of Dublin while we are still waiting many years for the long promised integrated ticketing system between the various services.