SlideShare has added Web conferencing to its site for posting, viewing, rating and commenting on business presentations, documents and videos, the company said Wednesday.The new SlideShare service, called Zipcast, is designed to be a simpler alternative to existing Web conferencing applications, according to SlideShare co-founder and CEO Rashmi Sinha."Web conferencing tools aren't up to par with consumer [online] products today," she said. "They're stuck in the 1990s. They require downloading, they're bloated and difficult to use.""We want to redefine the Web meeting experience with something modern, fast, simple and social," she added.Zipcast is browser-based, requires no software download and has been built using HTML5 capabilities. The service is integrated with the presentation- and document-sharing portion of the SlideShare site, so that users can call up an existing presentation and launch a Web meeting about it in an ad hoc manner. They can also upload new presentations up to 300MB in size.SlideShare has about 45 million unique monthly visitors to its site, most of them professionals seeking business information and contacts, according to the Sinha. They view about 3 billion slides per month.After registering with SlideShare, users get a unique URL for their online meeting "room" that they can share with an unlimited number of participants. There is no limit on how many meetings a user can host either.Meetings can be public or private. The meeting interface has sections for the shared presentation, group text chat and participant streaming video. Basic SlideShare accounts are free and include Zipcast meetings with one-way audio and video.Those with SlideShare Pro accounts, which start at US$19 per month, get additional features, including the ability to set a password for a Zipcast Web meeting and two-way audio.