If you just have a day in the area, I would say the best and most accessible sites to visit are <as href="http://www.themodernantiquarian.com/site/2474">Parknabinnia</a> wedge tombs, <a href="http://www.themodernantiquarian.com/site/2526"</a>Creevagh, <a href="http://www.themodernantiquarian.com/site/2471">Ballyganner South</a>, <a href="http://www.themodernantiquarian.com/site/1817">Poulnabrone</a>/<a href="http://www.themodernantiquarian.com/site/2477">Gleninsheen</a><a href="http://www.themodernantiquarian.com/site/2840">/Berneens</a> are all on the same road as are Parknabinnia and Creevagh (which is signposted as 'Leaba Wedge Tomb' on the side of the road).

If you have time to find more hard to reach places then Baur South and Clooneen are very nice. If your in the area for a few days then Lough Gur and Grange Stone Circle are less than an hours drive from Ennis if memory serves, on the other side of Limerick city. There's not much along the road from Dublin to Limerick unless you go way off the main road and even then its pretty scanty so I would concentrate on these two areas if I were you.