Calendar 365 and WhatWeekIsIt.org both provide good online calendars with week numbers. In addition to the current year, both websites can display the previous and the next years. Both calendars are available for free and do not require installation.
In addition to its desktop website, Calendar 365 offers a scaled-down calendar for mobile devices available at the same address. The website automatically detects mobile device access and adjusts the calendar accordingly. Calendar 365 also offers printable calendars in PDF format for free. The printable calendar is available with and without holidays marked. Click the tabs above the printable calendars to switch between the two options.