The present invention relates to lighting strips and more particularly to modular lighting systems comprising lighting devices, for example, lighting strips, physically and electrically connectable with one another by way of a plug and socket integrally formed at opposing ends of the lighting strips. The lighting strip devices can be made of flexible material to allow for applying the lighting devices along flat as well as contoured surfaces. The lighting strips can also be rigid. More particularly, embodiments of the invention include modular lighting strips comprising: a non-conductive substrate strip comprising an electrical circuit; a plurality of light sources operably connected to the electrical circuit; a plug integrally formed at an end of the substrate strip; and a socket integrally formed at an opposing end of the substrate strip; wherein the plug and socket provide for removable, friction-fit, latch or latchless, and electrical interconnection of two or more circuits. Also included in the invention are connector assemblies comprising the inventive socket and plugs integral to PCBs for use in the field of electronics. One or more lighting strip can be combined to form lighting systems, which are useful in many functional and decorative lighting applications. The lighting systems are useful for any residential or commercial application where modular, discrete, low-profile, and/or flexible lighting is desired. The lighting strips of the invention can be used in particular for back lighting, accent lighting, aisle or path lighting, contour lighting, elegant interior decoration, holiday decorations, or landscape lighting.