I'm putting in a bathroom in the basement and would like to know if there are any websites with plans on how to tie in to the drain in concrete floor for toilet,sink and vent.

Let me show you a typical, (in my area) bathroom group rough in. This configuation only uses one vent for the entire group.
4" ,(under cement and basements) 3" (on first and second floor) from the toilet to the main. The lavatory to connect to the toilet drain line and vent to the roof or revent back in the attic to a existing roof vent. The tub/shower to connect to the lavatory drain line and be wet vented by it as will the toilet. Be advised to always check local codes before changing or remodeling your drainage system. Good luck, Tom