This work proposes concepts, designs, experiences and lessons learned from some studies of ad hoc learning supported by wireless and mobile technologies. The ad hoc learning activity model supports learners communicating with or obtaining help from classmates or teacher, interacting with environment, and accessing teaching material from mobile device or Internet. Example scenarios with prototype systems for ad hoc learning are presented. Preliminary experimental and trial studies are conducted with these example scenarios in elementary and high school students. The potential impacts, limitations, and lessons learned in this study are also discussed from both the educational and technological points of view. Learning in a lively, vivid, and new learning environment, students are motivated with interests for learning the target domains. Ad hoc learning potentially extends the scope of learning activities and with more flexibility than in traditional school curriculum.