As many as you need to hook up to the router using Ethernet and Wireless. From there it's a matter of the bandwidth being shared with each laptop. Just keep in mind, the more wireless devices online, the more of a chance there is for the wireless connection to experience issues with slower speeds and some possible disconnects.
keep in mind that there is a setting for the maximum number of connections in the router settings (which you can change to accommodate the number you need), up to whatever the limit is.
additionally, it really doesn't matter whether they are connected via ethernet or wireless, the more devices you have connected, and the more each device is using the connection (including television if you are using that), the more bandwitch you will be using, so the slower your experience may become when you get many devices connected.
Just to clarify something from that last post ... while the STB's for FiOS TV do each allocate an IP address and use it to download guide data, this information is a very trivial amount. Watching regular FiOS TV does not impact the performance of the data network -- these are provisioned into seperate frequency spectrums do not impact one another.
DHCP server is set by default to allocate up to 254 addresses. There is also a limit to the number of connections through the firewall of 155309. This includes both active and some inactive connections as it may take awhile for them to time out. For instance at the moment with 1 device active and 1 set top I show I am using 196 connections. That number may also vary with your model of router.