The United States Olympic Training Center (USOTC) does not recommend specialized year-round training for sports or events. Advantage Athletics suggests core strength exercises and circuit training for your weightlifting for summer workouts that will help develop general physical fitness.
http://exercise.about.com/library/Core/bl_core.htm
http://exercise.about.com/library/weekly/aa100600a.htm
Pole vault specific strength and timing exercises are also good for the summer. I.e. swinging rings, gymnastics, horizontal bar, inverted rope climbing and rope vaulting...but not pole vaulting.
http://www.advantageathletics.com/polevault.html
Stay away from pole vaulting and sprint training...Instead do "Active Rest". Active Rest is playing lots of quick agility games. I.e. basketball, racquetball, handball, soccer... Surfing and/or swimming is also a good sport because it develops the total body extension muscles, shoulder range of motion and shoulder strength.
Summer pole vault camps are good because its about the only time most pole vaulters get chance to train with World Class coaches and just hang out with and socialize with large numbers of pole vaulters from across the country.
We suggest these things because that's what we learned from attending USATF Coaches Certification Clinics, the USOTC, AAF Coaches Clinics, coaching at the NCAA level with National Championship Winning Head Coaches (i.e. Art Venegas and Bill Webb) and many other coaching clinics put on by World Class coaches.
have fun!