This structure already appears with a different usage here: http://www.renshuu.org/index.php?page=grammar/individual&id=129

Maybe they could be merged together?

So, just to be sure, can this grammar be used with a noun which has been modified by an adjective? Like 'sad person' for example?

Don't laugh =(

They are similar, but one of the main differences it that らしい is based on conjecture: based on information you've gathered previously. っぽい can be something you say as soon as you see it.

Also, っぽい also has a lot of uses that just can't be used with らしい. I tend to think of when it's translated as "-ish", like blackish くろっぽい - this isn't something you'd say with らしい: it's a visual observation, not something that you'd say after considering other evidence/information.

Sorry about that! I'm pushing over the next couple of months to increase the number of model sentences, as they are sorely lacking in a number of places.

Sorry to bring up a 3 year old discussion, but with らしい　and っぽい... I usually hear people using っぽい when decribing something as being typical of what it is. 男子っぽい, 赤ちゃんっぽい, etc. So, this would be used for imediate reactions to something you see, rather than something that is typical all the time, such as 冬らしい, 先生らしい. These are based on the general concensus of what winter and teachers are usually like. From this, I kind of assumed っぽい　was a way of saying something is a lot like something else. (男子っぽい: Boyish, 赤ちゃんっぽい: Like a baby.) I also assumed that you could use っぽい to describe something as being like something it is obviously not, like calling a girl 男子っぽい. Is this interpretation of mine correct?