Eggman's "Aldura Campaign," if you aren't familiar with it, is a series of campaign maps set on the planet "Aldura."
While the campaign maps are all (relatively) short, they are very well-put-together and this particular download includes the first three missions, so the three put together may easily take you in excess of half an hour (which is a very decent amount of time).
The first campaign mission is, like the stock SWBF2 campaigns, a space mission set above the planet - it is a very simple introduction, but it is a nice one and works well to set the tone for the next two missions. The space map is nicely assembled and looks very polished, if somewhat simple.
The second campaign mission is set inside a city. It is an entirely linear map, but the script paces you well and it feels like a good recreation of a battle. The map is again simple but well-polished.
The third mission is probably the best of the three. It is another short mission set in a rainy "plains" area on the same planet (A planet with more than one environment? Blasphemy!). It's more of an "escape"-type mission (as opposed to the conquest-oriented mission of the second), and while the story is short, it is conveyed very well. One of the things I like best about this is that despite the map itself being centered around a very small area, there is one section in the campaign where you are asked to use a speederbike, and you actually must physically travel over a large plot of land - and it feels like you are actually doing this (in no small part because you are).
Conquest is also included with the last two maps. The "Aldura Campaign" is definitely worth a download. Try it out!