Online Siddurim

Kakatuv:
http://kakatuv.com/prayers.html

Shabbat and other important prayers with Hebrew and "interlinear translation" (shows word-by-word correspondence) and transliteration (Israeli pronunciation) in Orthodox, Conservative, and Reform versions. Page number correspondence to the most commonly used siddurim: Artscroll, Sim Shalom, and Gates of Prayer.

Interesting note: this very cool website was created by a convert to Judaism!

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Build a Prayer:
http://buildaprayer.org/

Interactive website that allows creation of a customized Shabbat services: Friday night, Saturday morning, Saturday evening, Blessing after meals.

Here is another -

http://www.chailifeline.org/siddur.php?gclid=CNH7wK7Z2rcCFY-Y4Aod9xQAWQ


There are also many online sites that have the "audio" but of course it is all in Hebrew.

The link to the JBC topic for online audio for services is:
JBC: Jewish Fundamentals> websites with audio for prayer services

You can add to it if you know of others.