Tropical Depression Erin was a tropical storm until earlier today, having weakened a bit due to a stable air mass surrounding it and oceanic temperatures that are marginal for tropical development. The result is a weak, but still distinct, area of low pressure in the East Atlantic. It's closer to Africa than us at this point but will continue to trek west-northwesterly over the coming days.
The good news is that Erin will not be a threat to the East Coast. Modeling suggests the system also stays weak and will likely work west-northwest over the next five days. It probably does not strengthen significantly as wind shear will increase in the coming days to offset a warmer ocean. In essence, Erin is going to be a dud of a tropical system overall.
However, the pipeline of possibility for tropical development is increasing with a number of disturbances traversing the Sahel (just south of the Sahara), working westward towards exiting into the Atlantic. The heart of the tropical season is the next six weeks and we will likely see a number of systems develop...unlike Erin, some of the next ones to develop will likely be stronger and track closer to North America.
Update: Erin was upgraded back to Tropical Storm status late last night. It's still weak, projected to remain so and also projected to weaken again in a few days in response to unfavorable upper level winds.