You can find 25 stotras dedicated to Lord Karthikeya from this page (Hindupedia.com). Few are in Sanskrit and few are in Tamil as well. Stotras are given transliterated English along with translations in English so that one realize what's being said in the stotras.
Names of few stotras are:
Kanda Guru Kavacham of Santhananda Swamigal
Kandhar Alankaram (Tamil)
Karthikeya Karavalamba stotram
Pragya Vivardhana Karthikeya Stotram
Shanmuga Kavacham (Tamil)
This resource will be useful for those who want to chant these stotras themselves.
Another similar site that I find useful is Bhartiweb.com. You need to go to the stotra section and do a search. I searched using terms like Karthikeya, Guha, Karthik, Shanmuga etc but none yielded any results. Finally I searched for Subramanya and this time the search yielded eight results.
Few stotras that you get from this site are: Subramanya Trishati, Subramanya stotra, Subramanya Ashtottara Shatanamavali etc.
I did a search just now on Youtube.com using the terms "Shubramanya Ashtakam" and it yielded many useful results. You can check those. If we use different search terms more results might be obtained.
You can hear Shubramanya Sahsranama (1000 names) here and Shubramanya 108 names from here.