Tumblezweedz, hi again !
There are two areas of Romania I haven't been to, and Constanta is one of them. I did go by the Black Sea, but in Bulgaria. So all I know, is probably what you already know : it's beautiful and... crowdy ! I tend to not go where tourists are... Excert from the Lonely Planet : "in midsummer the Black Sea coast ressembles a massive outdoor party, with beachfront barbecues and plenty of beer". This means though great ambiance !
Browse through the Eastern Europe Lonely Planet, they give detailed infos on 8 resorts along the Black Sea (one resort was left out). The area is called Dobruja. For lodging, you should pay over $30 Euros per room, but there are campings close to the resorts. There are 9 resorts, Mamaia is the largest. Some resorts offer health spa (Eforie Nord, Mangalia), others lots of sports and outdoor activities(Mamaia, ), or beach partys/nightclubs (Neptun-Olimp). Saturn, Venus, Aurora, and Jupiter are smaller and less expensive resorts.
The Danube Delta (cities : Tulcea, Maliuc, and Sulina) is the border with Ukraine. Reading the LP, it seemed pretty neet also. You can even sleep in houseboats. According to my LP (2002 edition), you need a permit in order to visit this area.
Has this helped ???