These days, creating web page is similar to using a word processing package. The main task is working out what you want to say and who it is for and therefore how often it requires updating. You'll then need to design and organise a set of pages, or "site", which reflects the needs of your intended audience.
Most Internet Service Providers or local community networks will give you plenty of free space on their servers. However, you may require additional services, such as mailing lists, databases and so on, which will cost more money. See SCIP's list for a summary of free services.
Once your pages are ready, you use FTP to transfer the files to your service provider, and they're then visible to the whole world. Remember that any interactive parts of your page, for example an email address, will need regular support.
! Unless you tell people, then your pages are unlikely to be found. There are mechanisms for letting the major search engines aware of your presence, and it's a good idea to tell any relevant national organisations, other local groups and networks, and to add your new address to publicity materials.
There's a great guide to developing web sites at Yale University