Right, so summer is here (in the UK :P), and I'm on a tight budget.
Anyone got any ideas on what I can do to entertain myself at home or with friends that doesn't require masses amount of money?

Paper craft? You can make some cool stuff and it keeps your hands busy, and is something that once you start, you never stop coming up with ideas for what to do next. I like paper mâché it's somewhat therapeutic lol but paper folding looks cool too.

if you have a transportation - this is my idea - take a day trip to a park or somewhere you do not go often - if you have a dog, take your dog hiking with you and see some beautiful things - im in the states so i don't know whats over in UK, or do some crafting - some are cheap - perhaps crocheting? it is alot cheaper than beading for sure, or read? make a summer list and read outside and get some color on you? perhaps learn to draw or if you already draw get a new sketch book and mark it as "2011 summer work" learn to paint?

i am now gonna be working full time through the summer - for my evenings i am going to be doing my readings for my book club, and crocheting Christmas presents (yeah a head start and less $$ to spend last minute or not rushing to get it done) and i will do it outside! :-D and because summer is here - i am taking an advantage for the weight loss to walk every morning at 5 am with my dog for a few miles before work.

good luck!

Go to the beach
Go walking (look online for routes)
Go to a new city and do some sightseeing
Go to a castle or other sight. Look at joining the National Trust as it gives large discounts to tourist sights.
Look online for local festivals/markets/concerts

RedFraggle said it all for me.. :)

Game night. Do it with coffee instead of booze. Or tea. Have a variety of teas to choose from. That makes it fun. Tea parties!

I've never really been on vacation before..my summers usually consist of:
Exploring, just pick a direction and start walking
Swimming-we swim in the river up the road from here
Have cookouts-invite some friends, tell them to bring their favorite foods, build a fire and roast hot dogs or something..
Or-pitch a tent in your front yard and go camping.

Of course, we live in the middle of nowhere and we are surrounded by trees, so we can do these things without intruding on neighbors..

Barbecue potlucks with your friends. Beer is cheap (at least here in the US), and everyone can bring something.

Letterboxing is cheap and fun. It's like an outdoor scavenger hunt.

Go to http://www.atlasquest.com to learn more about it.