I think that this is going to be as wide ranging as the topic itself. The reality is that assessment can take on different forms. It does not only need to be the formative exam or standardized test. This is one form of assessment. If a teacher has access to technology, I think that using an online learning environment such as moodle or edmodo might be a very good way to assess learning. In being able to generate student postings or thoughts on content, the teacher is able to gauge and assess comprehension in real time and offer insight themselves. This helps to establish a learning environment and a culture of learning where feedback and assessment can happen in real time.
Another example of assessment that can give the teacher a pulse of where focus is needed is with the exit slip. The exit slip has become a rather popular form of assessment. At the end of class, teachers ask students to write down their thoughts about a particular topic. If used well, the exit slip is able to allow the teacher to have their finger on the pulse of where instruction is and where instruction needs to be driven. The exit slip is another example of an assessment tool that allows the teacher to gain a strong read as to where students are.
I think that time is one of the biggest obstacles in assessment. We simply do not have enough time to effectively do what we need to do. One example of this in my own practice is how I have not been able to utilize the student conference regularly and effectively. The student conference is one way in which learning can be assessed through discourse and dialogue. The student- teacher conference can take on many different forms, but it is a very good tool for assessing where students are and where they need to be. It does not provide data that can be optically scanned, or presented in a grid like format, yet the student- teacher conference is an effective form of assessment because it talks openly and directly about student learning. In this, there is an assessment that is authentic and valid in that it is driven by and for the student and their needs.
In my classroom I use several ways to assess my students. I teach in Texas and my district uses the TPRI, DRA, and Star Reading (Renaissance software), to assess reading levels in the elementary grades. These help to determine leveling of the students for Guided Reading Groups. When the students are in their groups I informally assess on an ongoing basis. Based on these informal assessments, I plan mini-lessons. There are many formal and informal assessments going on throughout the school day.