Blog technology is a potential medium for encouraging reflective writing through self-expression and interactive exchange through social networking. This paper reports on a study using blogs as out-of-class assignments for the development of learners' language competence. The study involved seventeen university students at advanced level who kept personal blogs over a 14-week period. Data collected from blog pages, post surveys and final interviews reported affordances and challenges of using blogs for personal expression and collaborative interaction. The results showed that regularly creating blog entries had a positive impact on learners' writing fluency and increased their motivation to write for a broad audience. Importantly, a four-skill integrated approach to task-based activities afforded opportunities for students to use the target language for blogging. The findings also indicate that peer feedback on the content prompted further discussion, whereas linguistic feedback from the instructor encouraged focus on form for language accuracy. The study concludes that learners' critical thinking and technological skills are essential for the implementation of blog projects in L2 instruction.