I don't know of any other sites between Blue Lagoon and Scuba Ranch (Clear Springs) other than Athens, which is a bit out of the way. If there are any other sites along that route, I'm not familiar with them. Now there are some south of there. There's Twin Lakes in Manville right on Hwy 6, 288 Lake which I think is technically in Pearland, and Mammoth lake in Lake Jackson. If you want to go West of DFW, there's Wheeler Branch in Glen Rose, but there are no facilities there to get air refills so you would need to bring multiple tanks if you wanted to do more than one dive. There's also Possum Kingdom Lake but I havent' seen any recent dive videos there.We have several lakes here in and around the Metroplex, but you never see/hear of anyone diving them. I've yet to find a single Scuba Video of Lake Lewisville, which is minutes form my house. And I'd assume you could find many "treasures" diving the party cove there, but I have no idea what visibility is like and can't find anyone that's even attempted a dive in it.
If you come across any "new" sites, definitely post them up, as I'm looking for more places to dive aside from Clear Springs. I'm in a DM program and I think we're talking about going to Arkansas to dive Lake Ouchita and then likely Lake Travis. My instructor also mentioned another springs site in the CenTex area that's not Aquarena Springs and doesn't require their Eco certification course. So Kinda looking forward to that one, too.