Do all the exercises, that is how you practice

If the program does something useful for you, its a bonus

Forget about making a useful contribution, it requires more though and experience than you have :) you'd have to conduct a survey to find something both/easy/and/needed

Here are links of links of links ... on learning to program
General Computer Science: For Beginners
Where Do I Go Next?
Re: Reading other people's modules and codes
Re^8: How to use wxHtmlEasyPrinting (On debugging, verify everything, talk to teddybear ... and links and links
Re^3: highest value in hash (virtual teddybear)