Introduce yourself or state your name when speaking at least the first few times depending on meeting size. Don't assume that your attendees automatically recognize your voice. As with any meeting, limit side conversations.
Introduce guest speakers so everyone knows their voice and face too.
Mute your phone when you are not speaking. There is nothing worse than hearing the sound of someone typing away letting everyone know that they are only half-listening. Avoid cell phones and speakerphones when possible. However, speakerphones (such as a Polycom) designed for conferencing are acceptable.
If you are using a webcam, make frequent eye contact with the camera. This will help the remote people feel more a part of the meeting. If you are not using a webcam, uploading a JPEG of yourself into a Share pod can achieve many of the same goals with less of a bandwidth requirement. As the host of the meeting, a picture can help you connect with attendees.
Open your web meeting 10-15 minutes early with a lobby slide or rotating lobby slides confirming the meeting details (start time, audio information, agenda, etc.). This will also give those unfamiliar with web conferencing a chance to understand the interface and interactive abilities.
Include a Q&A. Encourage questions.
Highlight key points in your presentation. Use the tools to mark up to stress points.