Electricity.
Here in Ireland up until 2009 there was only one supplier of domestic Electricity (ESB) . In 2009 both Bord Gais and Airtricity entered the domestic Electricity market with lower prices.
ESB , Bord Gais and Airtricity are the 3 residential electricity suppliers in Ireland. The two newer companies have undercut ESB and are spending lot's on advertising campaigns to try and get new customers. Since mid 2011 ESB prices are no longer set by the energy regulator and they are allowed to set their own prices now

See more here about Cheapest Electricity Prices in Ireland .

Natural Gas is becoming more widely available in smaller towns - previously it was only available in cities like Dublin, Cork Limerick and Galway. Bord Gais is the semi state supplier - but it now has three competitors - Flogas , Airtricity and ESB (Electric Ireland) also supply gas to residential customers.

See this Comparison of Gas Prices in Ireland.

Heating Oil (kerosene usually) is still one of the major fuels for home heating outside the cities. Solid fuels like turf/peat wood and coal still play an important part too. Wood pellets are becoming more popular since the government introduced grants to assist with installation costs.
Heating oil prices in Ireland in mid 2011 were around 84c per litre including VAT .

Most Fuel prices in Ireland rose in 2010 because of a new Carbon Tax introduced in the December 2009 Budget
More about Carbon Tax in Ireland here