Here are a few comments on the current documentation of the plugins:

- The table at the top of the page should be updated to include the latest list of snippets distributed with gedit.
- Maybe link the items in the table to their corresponding descriptions lower on the page

Some pointers on the snippets documentation:
- I think it should be explained that the 'n' in ${n} is actually a number and that the number defines the order in which the placeholders are visited when pressing tab (or shift tab)
- It might be worth mentioning that <Shift>+Tab moves the cursor to the previous placeholder instead of the next
- Instead of ${n} just use $n (which is the simplest way to define a placeholder)
- There is a small typo in the mirror placeholders section:

Mirror placeholders
    A repeated _a_ tab placeholder

- The somewhat special $GEDIT_CURRENT_WORD environmental variable should also be mentioned (see l.g.o. for more information on that env var)
- A small typo in the basename env var description:

The full filename of the document, or _and_ empty string if the document isn't saved yet.

- In the tab placeholders section:
Pressing Tab when there are no more tab placeholders moves the insertion cursor to the end of the snippet text.
-> This is only true if no end placeholder has been defined manually. An example
could be a for snippet:

for (${1:i = 0}; ${2:i < n}; {$3:++i}) {
    $0
}

Besides these rather small pointers, great work!