Man if those people make you feel embarassed for laughing infront of them, you really don't want to stay friends with them! That's crazy- I'd be insulted if none of my friends ever laughed at what I said! Even if I snort or snot or spit out my drink from laughing too much, I'd never expect my friends to think any less of me.
The only time I was embarassed because I couldn't stop laughing was when I went on holiday with people I didn't know very well, who were older than me and a couple of them are the funniest people I've ever met. I'd be pi**ing myself laughing for ages after everyone had stopped which made me feel pretty 'uncool' but I got over it, I wouldn't say it made me feel horrible or uncomfortable- they were probably flattered and the worst they thought was that I was very childish.