Laura Robson of Great Britain is currently ranked #254 but she has reached the second round of Wimbledon 2011. I think she was allowed into the main draw because she's British and she didn't have to go through qualifying. Anyhow, she made good use of that opportunity and promptly won her first round match against Angelique Kerber of Germany, 46 76(4) 63, who is ranked much higher than her, at #77.
However, her opponent in the second round - Maria Sharapova - is more daunting. Even then, at least she would get the chance to play with a Grand Slam champion, something she won't experience in the ITF circuit. I'm sure she would learn a lot from that experience.