I wouldn't blame your host, actually. It's WordPress. It's a shame it's so often given a free pass on these issues when it really isn't good at handling peaks in traffic.
Using the popular caching plugins...W3 Total Cache (http://wordpress.org/plugins/w3-total-cache/) or Super Cache (http://wordpress.org/plugins/wp-super-cache/) seem to be well liked and I've used both of them without too many issues (I have some weirdness in my WP upgrade path). My blog has been on HN and reddit a few times and has never crashed, even though I'm on the cheapest Dreamhost hosting plan with what seems like 5 to 10 second response times for non-cached pages.
