Notes about some of the spellcheck programs I've tried out. By far the best of these is Firefox.
Firefox 2.0 has a built in spellcheck. And it works!
Spell as you type
Red underlines for words not in your dictionary
Right click on misspelled word has suggestions in the first popup menu, so no hunting down the right word.
Appears to have a dictionary shipped with it so spellcheck is fast and does not involve long discussions with Google web servers.
When shipped, it will halt spellchecking after reaching 500 misspelled words. This is insufficient for an article with tons of foreign language words like Tokyo. Type about:config in the URL bar and then find the entry for extensions.spellcheck.inline.max-misspellings and change it to a large value.
When in en-US mode, it complains about Commonwealth spellings
The "red underlines" on misspelled words is fine for typing stuff yourself. But if you want to spellcheck a full article written by someone else it really isn't a "loud enough" marker so your eyes are strained a bit trying to find the misspellings.
Only works on Internet Exploder on Win32.
No "highlight mispelt wurds" feature. (I.e., no red-underlines).
On long pages, frequently goes insane so that you cannot see the context of the word whose spelling is in question. If you continue when this happens, it will royally screw up the page text
Modal spellcheck dialog so you cannot edit the page text or even scroll the page while the spellcheck window is up. And of course, if you close the spellcheck window, next time you spellcheck you get to start over from the beginning yet-again.
Konqueror, the KDE Web browser. Available mostly on Linux, but can be installed on other platforms too. Spell check is available only if the KDE spelling module is installed.
Spell as you go in the browser
No way to highlight a word with the mouse and check its spelling. All you get is red-underlined or no red-underline. The spell check dialog box only works on the entire page, and is the only way to get suggestions for the correct spelling.
Slow. So if you correct a red-underlines word, it 5-10 seconds before you are certain it has rechecked the spelling.
Unreliable dictionary. The dictionary has bogusness in it, and it is not obvious how to fix this. Mispelled words are often not flagged. Correctly spelled words occasionally are flagged and the suggestions include mispellings.
Spell check dialog box is modal. No scrolling for you!
Multiplatform Firefox extension
Royal pain in the neck to install
You get two choices: word-wrap or non-word wrap. If you choose word wrap, the program edits gratuitous newlines into the text. If you choose no wordwrap, you get a horizontal scrollbar which lets you see the rest of the text. Apparently it didn't occur to the author that a GUI could wrap text without actually editing the text.
World's slowest "Ignore All" button
World's slowest "Add to dictionary" button
Minor nit: If you want a spell-checking context menu for a red-underlined word, you must double click to select the word first.
Does not spell check in the text entry window consistently. You must bring up the spell check dialog which contains a copy of the text in it.
Google Toolbar. This extension contains a spell-check module.
Excellent colors used for word highlighting. My eyes frequently miss a "red-underlined" word on white background -- which is the default for many of the other tools. This tool has colors and fonts chosen such that I see every mispelling without effort.
Non-traditional user interface. Spell check is modal, and you left-click on mispelled words to get a popup-menu of options.
Gives up. There seems to be a limit to how many misspelled words it will check. When spellchecking a travel page in a non-English country, each non-English placename or sight-name counts against this maximum. Once the max is reached, no checking is done further down the document.
Spastic. When you click on stuff, the text frequently lurches around in the text edit box. Very annoying.
"Add to my dictionary" apparently means "don't warn me about this word ever again". It does not mean the more familiar "this is spelled correct and you should consider offering this correction to me in the future."