Here's what I found on a quick google search. There probably are a lot of duplicates as I used different search phrases. Next step is to evaluate each link.
most useful for learning
https://sites.google.com/site/marekhlavac/slovak_lessons_beginner_overview
http://slovake.eu/en/learning
overview
http://en.wikipedia.org/wiki/Slovak_language
some miscellaneous learning
http://www.slovak.com/language/ ok. overview, alphabet, numbers, greetings, calendar, phrases, vocabulary
http://www.omniglot.com/writing/slovak.htm combined with other languages, overview, phrases, numbers colours, kinship terms, songs
http://wikitravel.org/en/Slovak_phrasebook
games/ flashcards
http://www.digitaldialects.com/Slovak.htm
http://www.quia.com/jg/435090.html
general
http://www.ethnologue.com/country/SK
http://www.slovak-republic.org/language/
http://www.kwintessential.co.uk/resources/global-etiquette/slovakia.html
http://www.britannica.com/EBchecked/topic/548978/Slovak-language
http://en.wikipedia.org/wiki/Category:Slovak_language
Not sorted yet
http://slovakia.embassyhomepage.com/slovak_language_learn_slovak_language_schools_slovak_dictionary_online_holiday_phrases_in_slovak_embassy_london_uk.htm
http://www.ssees.ucl.ac.uk/languages/slovaklang.htm
http://www.lmp.ucla.edu/Profile.aspx?LangID=47&menu=004
http://www.slovakia.culturalprofiles.net/?id=-6840
http://en.wikipedia.org/wiki/History_of_the_Slovak_language
http://www.barnesandnoble.com/s/?category_id=1288455
http://answers.yahoo.com/question/index?qid=20101221230515AAWlksX
http://mihu2.tripod.com/micro/language.htm
http://www.cdvuk.sk/blade/index.php?c=351&summer-course-of-slovak-language-and-culture
http://webtranslation.paralink.com/Slovak-language_Slovak-English_Translation/
http://sobipro.sigsiu.net/download/languages/164-Slovak-Language
http://www.sbs.com.au/yourlanguage/slovak/
http://www.seelrc.org/webliography/slovak.ptml
http://www.meetup.com/czech-150/
http://www.omniglot.com/books/language/slovak.php
http://localize.drupal.org/translate/languages/sk
http://www.lexilogos.com/keyboard/slovak.htm
http://www.omniglot.com/language/phrases/slovak.php
http://www.linguanaut.com/english_slovak.htm
http://mylanguages.org/slovak_phrases.php
http://www.slovakiasite.com/useful-vocabulary.php
http://www.linguata.com/slovak/Basic_Slovak_phrases.html
http://en.wiktionary.org/wiki/Category:Slovak_phrases
http://www.bratislavaguide.com/slovak-language-basic-phrases
http://www.bbc.co.uk/languages/other/quickfix/slovak.shtml
http://www.slovak.com/language/phrases/phrases.html
http://mylanguages.org/learn_slovak.php
http://www.slovakiasite.com/slovak-language.php
http://www.lingvozone.com/Slovak
http://www.slovensko.com/about/is-slovak-difficult
http://www.youtube.com/watch?v=ap6b04JkVYI
http://en.wikipedia.org/wiki/Slovak_declension
https://sites.google.com/site/marekhlavac/slovak_lessons_beginner_overview
http://www.dielna.net/slovakgrammar_en.php
http://www.opakovanie.sk/index.php?topic=133.0
http://forum.wordreference.com/showthread.php?t=775362
http://www.ccjk.com/resource/slovak-translation-services/slovak-grammar/
http://www.antimoon.com/forum/t15083.htm
http://mylanguages.org/slovak_verbs.php
http://en.wiktionary.org/wiki/Category:Slovak_verbs
http://learn101.org/slovak_verbs.php
http://www.heartofeurope.co.uk/dictionary_verbs.htm
http://groups.yahoo.com/group/Slovak-World/message/19732
http://quizlet.com/subject/slovak-verbs/
http://en.wikipedia.org/wiki/Slovak_language
http://www.101languages.net/slovak/ ***
http://www.surfacelanguages.com/language/Slovak *
http://www.amazon.com/Talk-Now-Learn-Slovak-Beginning/dp/B0000899QX
http://www.mylanguageexchange.com/Learn/Slovak.asp
http://www.digitaldialects.com/Slovak.htm ***
http://www.masteranylanguage.com/cgi/f/rView.pl?pc=MALSlovak&tc=Games&vm=fc&la=
http://www.purposegames.com/game/slovak-language-quiz/info
http://www.byki.com/fls/free-slovak-software-download.html
http://www.studystack.com/flashcard-76598
http://quizlet.com/15956098/slovak-irregular-verbs-flash-cards/
http://www.masteranylanguage.com/cgi/f/rView.pl?pc=MALSlovak&tc=Verbs&vm=fc&la=
http://www.livemocha.com/flashcard_sets/view/672581
http://www.byki.com/lists/slovak/10-fero-irregular-verbs-present-tense.html
http://www.androidpit.com/en/android/market/apps/app/com.iedutainments.ipad.sl.free/FREE-Slovak-Verbs-LearnBots
http://www.flashcardexchange.com/cards/slovak-english-2386032
http://mylanguages.org/slovak_words.php