The pilot received a weather briefing which forecast IFR after 1800 EST. He departed DCA in light drizzle conditions. Approximately 35 miles from DCA, radar service was terminated and the pilot attempted to contact ATC to no avail. He reported that near the BROOK VOR, the VOR needle was moving sluggishly and the ammeter showed a strong discharge. The pilot stated he noted the DG not working. Due to the decrease in ceiling, he made a descent to 1000 ft MSL to remain VFR. After 2 or 3 minutes, the pilot made a 180 degree turn to remain VFR and noted the ceiling had decreased around him and he was in an open area approximately 1 to 2 miles wide. During the turn, the pilot noted the artificial horizon tumbled. He elected to make a precautionary landing on a road during which the left wing contacted a stop sign resulting in substantial damage. Post accident inspection of the aircraft failed to reveal any failure or malfunction of the electrical or vacuum system other than the battery was nearly drained.