Telehub Map from Stillman Telehub, 12-13-2005, from the Second Life Wikia - the red pins mark "Points of Interest" rather than telehub locations. You can see that Second Life was still relatively small then.
In late 2005, Linden Lab removed most Telehubs on the grid, opening the way for "direct teleport" from one point to another. Some of the telehubs were converted into Infohubs, meant to be community gathering spaces and "welcome areas" for new Residents.
Waterhead Infohub, formerly a Telehub
The new infohubs were now intended to be places where residents could set a home point, and where they could meet other residents and socialize. New infohubs have been built as Second Life expanded. Many infohubs have tutorials and other information for residents, or they may have a nearby NCI infonode (smaller version of the information at the Main NCI locations). Many infohubs are being maintained by residents, so there is a tremendous variety of build from infohub to infohub. During my visits to collect slurls and landmarks I found most of the infohubs had visitors, with a mixture of new and old residents.
If you are curious about what these Telehubs looked like, you can visit the Waterhead Infohub, or you can get a package of three different telehub models at the Stillman Bazaar.
This is the poster I made for the Tourist Information Office. It shows an old telehub on the top, and the Waterhead Infohub on the bottom.
Here is a list of infohubs on the Mainland I got from the Second Life Wiki, with my notes. If the landmarks don't work, just put the sim name in the World Map, and look for the symbol. You can also just put "Infohub" in the space on the World Map. You can get a copy of a notecard with Landmarks in the Tourist Information Center in Cecropia.
Hanja in Gukyeol
The Old Teen Welcome Area in Card
Old Governor's Mansion in Clementina http://maps.secondlife.com/secondlife/Clementina/184/123/61
Mahulu Infohub near Mount G'Al Volcano - you can take a balloon ride from the roof!
Mauve Infohub -
Miramare in Nova Albion /Barcola
Chalet Linden in Wengen snow area - one of my favorites! - Lots of winter activities there.
Korea 1 in Korea1 - There is a teleport board listing "Sister Cities and Friends" - although some locations seem to be out of date.
Barbarossa Ferry Terminal & Infohub - pick up a free sailboat!
Bear Dream Lodge in Bear - Weasels and watermelon critters, and bears, oh my!
Boardroom Infohub and Conference Center
Braunworth Infohub - refurbished industrial ruins
Castle Valeria - I find the castle a bit gloomy; the other side of the island is more cheerful.
Degrand Infohub - little island with lighthouse - if you have a boat you could sail from here. There are interesting underwater features such as the Lost Treasures of the Sunken City in Sarante.
Hau Koda - Bay City Municipal Airport - http://maps.secondlife.com/secondlife/Hau%20Koda/68/60/25
Helfell InfoHub - Fuerte de San Phillipe nearby is also a Linden Public Area - if the drawbridge is up, touch it to lower it.
Hyannisport Infohub - in my opinion one of the most beautiful of the Infohubs
Hyles Swamp in Hyles
Iris Moth Temple - Linden Historical Site
Isabel Infohub - the very popular Shelter is just north of here
Moose Beach Infohub
Waterhead Welcome Area - This is a recreation of a telehub. You can get a copy of the original telehub model at the Stillman Bazaar.
Zebrasil Infohub, billed as "The village in the shadow of terrible volcano!" The volcano goes off about every hour and is quite nice. Explore under the sea nearby for wrecked ships.
ADULT: (I found these crowded and boring)
Arapaima Safe Hub -
Nelsonia Safe Hub
Oritz Dam Infohub
Listed as 'Former' or 'Inactive' (These were more interesting and worth visiting)
Anzere Infohub - By the Confederation of Democratic Simulators - a virtual democracy
Calleta Hobo Railroad Infohub - this whole area is fun to explore
Hanson - this Infohub was converted to parkland, but there is a gingerbread cottage and sled ride over the bridge and up the hill, and also penguin/moles.
Murray Infohub - this was rebuilt in 2010 and has many sims to explore nearby. Look for the ghost town and the vehicle testing tracks - also, beware of landsharks...Free sailboat at the dock - or an innertub if you're not that adventurous.
Plum Welcome Area - Preserved old Welcome Area, including the notecards...
Ross Memory Bazarr @ Ross Infohub - lots of interesting things here.
Violet Infohub - always seems to be some kind of argument going on when I am there, but very popular...
Warmouth Infohub - the Nerditorium
Olive - Great Second Life Railway Station, with frequent trains - take a trip!
Periwinkle Station - go down the stairs to visit a lovely garden and rest area. There are some freebies on a floating gazebo.
Those are all the Mainland Infohubs I know that are open to all residents. Have fun!
Free copy of Waterhead Telehub