If terran, place 2 or 3 SCVs on the ramp and a marine or 2 (depends on how many u get before the rush arrives) behind the SCVs. The zerglings will try to attack the marines because of their AI, but the SCVs are blocking the way.
As protoss, do a 9 & 10 gate build and get zealots fast. Place 2 or 3 zealots on the ramp and HOLD POSSITION! Do not try to run after the zerglings. If the zerglings arrive before u get 3 zealots, bring 2 probes to the ramp to block and help attacking. If he gets into ur base with 6-7 lings u should be pretty screwed.