Currently there are several wireless technologies for mobile data applications. One of the important issues in any mobile technology is how hand off is accomplished. This paper studies the handoff mechanisms in some of these popular technologies and details their pros and cons. Experimental results will be shown where ever available. Handoffs in following technologies are considered: 802.11, Mobile-IP, GPRS, and CDMA-EVDO. These technologies have take different approaches based on their design goals and expected applications. How these different mechanisms impact their performance in different situations will also the detailed. The interworking issues among these technologies will also be mentioned in the paper.