Find a single parent group and hunt out other single mums. I think most of us find it hard at weekends. Do you take the kids to any sports at the weekends? I have started to take my DS to football again and it's great as it breaks up the day and I have met a few mums that way.
The single group I am part of has a facebook group and people just post they are free and does anyone want to meet up. It is a good way to meet new people and because everyone is in the same boat it is quite supportive. It also means that if there is anything going on locally you always find out about it and have people to go with.
In May there are 18 single parent families going to Elderflower festival and camping from my group!
I know how you feel though and it can be a bit depressing. Summers just around the corner though
I find them hard sometimes too, I work Saturdays so only Sundays I feel it. I usually visit family or take dd to see her nan (Exdps mum) the time I hate the most though is about 4ish, most playgroups have finished, weathers usually crap or dark, it's too early to start doing dinner and for some reason it's when I feel most alone...don't really have any suggestions but just want you to know your not alone.
I am finding weekends and public holidays really, really hard....It is not so much the lack of a break from the kids, it is the doing it all on my own. During the week/holidays I can pair up with sahm friends and will sometimes have a friend over for a dvd etc after kids are in bed but weekends everyone is involved in their own family and same with public holidays....finding them hard