If you are into spelling games like Scrabble, the first thing you would noticed that in the WP7 marketplace, popular titles on the iPhone/Android phones like Word with Friends are missing. Personally I am just glad Zynga hasn't invade the WP7 spaces with virtual cows and imaginary chickens.
There are 3 excellent spelling type games that you should definitely have on your WP7 handset. Best of all, they are all FREE!
Spell It is one of the original scrabble type game to appear since the launch of WP7. Large user base means that you don't have to wait forever after starting a game for your opponent to respond. Support games up to 4 players. Like all the non-scrabble word games, it has it's unique board layout. Supports fast app switching! Click here to install
I had played word with friends but one of my biggest complaint (also my friends) is that it doesn't keep track of how you are doing against each other. Words BY POST changes that by keeping records against your opponents so you know how badly you are beating your friends or how badly they are kicking your ass.
Your friends don't have WP7 devices? other than "convincing" them they should get with the program and get a spiffy new WP7 device, Words BY POST are also available on iPhones and Android handsets so you can challenge your friends on other mobile platforms. You can invite your friends via facebook posting as well.
Words BY POST is an ad driven app but does have a paid version that is Ad free. Get it here
Wordament is an unique spelling where at any given moment, you are challenging all the other players on the Interwebs who are playing the same game at the same time. 2 mins to swipe and spell all the words you can find on a 4x4 tile board.
Fast face, addictive and fun. Definitely worth a try. Get Wordament here