御中元 ochuugen is the custom of summer gift giving. In my local stores, there is a huge display with aisles of summer gifts. You may also see the something like 夏のギフト (natsu no gifuto summer gift) or even サマーギフト (summer gift spelled in katakana).
This gift-giving season typically corresponds to Obon. In Okinawa, it is traditionally observed when visits to the family home are made during Obon (customarily the second day), but it is okay before or after. Especially in the workplace where you will probably not see them during actual Obon.
For me, the most interesting part is the types of gifts on display in stores. Popular items are summer fruits (mango in Okinawa), rice, coffee, pork, unagi (eel), jelly sweets, and other goodies. But there are also gift sets such as laundry soap, beer, spam, cans of tunafish… sometimes I find them quite odd, as far as gifts, but it seems so practical that I actually sort of appreciate it. Usually gifts are about 2000 yen to 5000 yen; stores make a lot of money during this time period. It is also typical to ship gifts to family members who live far away… during this time I see many people filling at shipping forms at the store counters for summer gifts.